Lack of Efficacy of Two Consecutive Treatments of Radioimmunotherapy With 131I-cG250 in Patients With Metastasized Clear Cell Renal Cell Car
http://www.100md.com
《临床肿瘤学》
the Departments of Nuclear Medicine, Urology and Oncology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
Wilex AG, München, Germany
the Department of Radiology, Rijnstate Hospital, Arnhem, The Netherlands
ABSTRACT
PURPOSE: A previous activity dose-escalation study using 131I-labeled chimeric monoclonal antibody cG250 in patients with progressive metastatic renal cell carcinoma (RCC) resulted in occasional therapeutic responses. The present study was designed to determine the safety and therapeutic efficacy of two sequential high-dose treatments with 131I-cG250.
PATIENTS AND METHODS: Patients (n = 29) with progressive metastatic RCC received a low dose of 131I-cG250 for assessment of preferential targeting of metastatic lesions, followed by the first radioimmunotherapy (RIT) with 2220 MBq/m2 131I-cG250 (n = 27) 1 week later. If no grade 4 hematologic toxicity was observed, a second low-dose 131I-cG250 (n = 20) was given 3 months later. When blood clearance was not accelerated, a second RIT of 131I-cG250 was administered at an activity-dose of 1110 MBq/m2 (n = 3) or 1665 MBq/m2 (n = 16). Patients were monitored weekly for toxicity, and tumor size was evaluated by computed tomography once every 3 months intervals.
RESULTS: The maximum-tolerated dose (MTD) of the second RIT was 1,665 MBq/m2 because of dose-limiting hematological toxicity. Based on an intention-to-treat analysis, after two RIT treatments, the disease stabilized in five of 29 patients, whereas it remained progressive in 14 of 29 patients. Two patients received no RIT, and eight of 29 received only one 131I-cG250 RIT because of grade 4 hematologic toxicity, formation of human antichimeric antibodies, or disease progression.
CONCLUSION: In patients with progressive end-stage RCC, the MTD of the second treatment was 75% of the MTD of the first RIT. In the majority of patients, two cycles of 131I-cG250 could be safely administered without severe toxicity. No objective responses were observed, but occasionally two RIT doses resulted in stabilization of previously progressive disease.
INTRODUCTION
With almost 12,000 cancer deaths each year in the United States, renal cell cancer (RCC) accounts for approximately 2% of all cancer deaths.1 Approximately 25% of the patients present with metastatic RCC, and up to half of the patients diagnosed with disease confined to the kidney will ultimately develop metastases.2 Because responses to chemotherapy are poor, there is no role for treatment with chemotherapeutics in these patients.3 Likewise, radiotherapy is only given as palliative treatment of symptomatic metastases. Currently, immunotherapy with interleukin-2 and interferon-alfa, alone or in combination, is the only treatment with curative intent that is available for patients with metastatic RCC, although responses are modest and in the range of 5% to 25%.4,5 Therefore, there is a need for the development of new strategies for the treatment of metastatic RCC.
We aim to develop an effective radioimmunotherapy (RIT) strategy for metastasized RCC using the chimeric monoclonal antibody (mAb) G250 (cG250).6,7 cG250 is a high-affinity (Ka = 4 x 109 M–1), chimeric, immunoglobulin G1 (IgG1) mAb, reactive with the G250 antigen.6,8 The G250 antigen has been identified as carbonic anhydrase isoenzyme 9 (MN/CA IX), a transmembranous glycoprotein.9-11 The antigen is expressed on the cell surface of the majority (> 95%) of clear cell RCCs.12 Approximately 80% of RCCs are of the clear cell type. The reactivity of mAb cG250 to normal human tissues is restricted to the gastrointestinal mucosa and gastrointestinal structures (bile ducts, pancreas).8,13
The chimeric version of the mAb has been developed to reduce its immunogenicity, allowing repeated injections.6 Several clinical studies with 131I-labeled cG250 have been performed. In tumor-targeting studies with radioiodinated cG250 in patients with RCC, Steffens et al14,15 demonstrated that focal uptake of 131I-cG250 in RCC lesions can be extremely high (up to 0.52%ID/g), confirming that potentially high radiation doses can be guided to RCC lesions. In the subsequent phase I activity-dose escalation study, the maximum-tolerated dose (MTD) in patients with metastatic RCC disease was established at 2220 MBq (60 mCi)/m2 131I-cG250.7 In one patient, stable disease was achieved, whereas another patient showed a partial response.7 Divgi et al16 recently reported stable disease in approximately half of the patients treated with fractionated 131I-cG250. However, they did not find evidence for fractionation-induced sparing of the hematopoietic system.16 These studies confirmed the feasibility of repeated dosing of the chimeric version of the antibody.6,7,16
Based on the phase I results,7 a phase I/II study was designed to establish the response rate (phase II) of patients with progressive metastatic RCC treated with high-dose 131I-cG250. The RIT treatment was expanded with an additional RIT treatment to increase the antitumor effect. Because a second RIT of 131I-cG250 had not been given to patients previously, the MTD of the second RIT had to be established first (phase I). Herein, we report the safety and efficacy of two consecutive treatments of 131I-cG250 at MTD in patients with metastatic RCC.
PATIENTS AND METHODS
Patient Characteristics
Twenty-nine patients with clear cell RCC (median age, 57 years; range, 40 to 72 years; 20 men and nine women) were included (Table 1). All patients had undergone a tumor nephrectomy in the past and had measurable progressive disease at the time of enrollment. Participation in the trial was allowed only after at least 6 weeks had passed since the last course of any anti-RCC therapy. Simultaneous treatment with anti-RCC drugs while enrolled onto the study was not permitted, except palliative external beam radiotherapy. Patients had to be older than 18 years of age with a Karnofsky performance status greater than 60. Patients with untreated hypercalcemia, allergic diathesis, significant arrhythmia, complete bundle branch block, electrocardiographic evidence of recent myocardial infarction, life-threatening infection, liver and/or renal failure, fewer than 3.0 x 109 leukocytes/L, fewer than 100 x 109 platelets/L, progressive CNS metastases, or a history of a second malignancy other than treated squamous/basal cell carcinoma of the skin were excluded from the study. In addition, women could not be pregnant or lactating. Patients who dropped out of the study were replaced. The study was closed after 15 patients had completed radiologic and hematologic follow-up 3 months after the second RIT treatment of 131I-cG250 at MTD (estimated size for determining a response rate of 30% [ .05 and ? .20]). The study was approved by the Medical Ethical Committee of the University Medical Center Nijmegen and the institutional review board of the Ludwig Institute for Cancer Research. Before study entry, written informed consent was obtained from all patients.
Monoclonal Antibody cG250 and Radiolabeling
Clinical grade cG250 vials (5 mg/mL) were obtained from The Ludwig Institute for Cancer Research, New York, NY. MAb cG250 was radioiodinated with 131I (MDS Nordion, Fleurus, Belgium) according to the IodoGen method, using a remote system, as described previously.6,7 Diagnostic (tracer) injections consisted of 220 MBq (6 mCi) 131I-cG250 (protein dose, 5 mg). The radioactivity dose of a 131I-cG250 RIT treatment differed for each patient (dosing depending on activity-dose level and body surface area), but the cG250 protein dose remained constant at 5 mg/injection.
Study Design
Within 30 days before study entry, a baseline computed tomography (CT) scan of chest and abdomen was obtained for all patients to adequately monitor the size of metastases. Before the first radioiodinated mAb cG250 administration, evaluation consisted of medical history, physical examination, and blood samples for routine blood chemistry, hematology, and thyroid function. To prevent 131I uptake in the thyroid, patients received potassium iodide and potassium perchlorate. All patients received a diagnostic IV infusion of 131I-cG250 (total volume, 10 mL) followed by acquisition of four whole-body scintigraphic images directly after, 2 to 3, 4 to 5, and 7 days after injection. The images were recorded using a double-headed gamma camera (MultiSpect 2; Siemens Inc, Hoffman Estates, IL), equipped with parallel-hole high-energy collimators (symmetric 15% window over 364 keV; scan speed, 5 cm/min [days 0 and 2/3 after injection] and 4 cm/min [days 4/5 and 7 after injection]) and stored digitally in a 256 x 1,024 matrix. If accumulation of the antibody in metastatic lesions was visualized and the tumor-to-background ratio of at least one of the metastases exceeded 1.5 at day 2 to 3 or 4 to 5 after injection, patients received the first high dose of 131I-cG250 (RIT 1; total volume, 30 to 40 mL) 1 week after administration of the diagnostic dose. The activity dose of RIT 1 of 131I-cG250 was 2,220 MBq (60 mCi)/m2, based on the activity-dose escalation study of Steffens et al.7 Approximately 1 and 2 weeks later, additional whole-body scintigraphic images were recorded (scan speed, 10 cm/min and 4-5 cm/min, respectively). Toxicity was monitored weekly and scored according to the common toxicity criteria (CTC version 2.0) until a definite rise in platelet and leukocyte counts was observed. Clinical follow-up, including laboratory parameters and a repeat CT scan, were performed 12 weeks after the first 131I-cG250 RIT infusion. Irrespective of the outcome of the CT scan evaluation, the same procedure was repeated 3 months after the first RIT treatment unless the patient had experienced grade 4 hematologic toxicity. The second diagnostic infusion (220 MBq/5 mg 131I-cG250) was mainly administered to rule out the presence of human antichimeric antibodies (HACA) that would lead to rapid clearance of the radioiodinated antibody from the blood and body. When this was not observed, patients were treated with a second high dose of 131I-cG250 (RIT 2).
Because there is no experience with a second high-dose injection of 131I-cG250, the MTD of RIT 2 was established first. Before the start of the study, three dose levels were predefined for dose escalation of RIT 2: 1,110 MBq (30 mCi)/m2, 1,655 MBq (45 mCi)/m2, and 2,220 MBq (60 mCi)/m2. Three patients per dose level were entered. If no dose-limiting toxicity (DLT) was observed at a particular dose level, the next three patients were entered at a higher dose level. The MTD was defined as the dose level below the dose at which DLT occurred. If no DLT was observed at the third and highest dose level, MTD would be set at 2220 MBq (60 mCi)/m2. DLT was defined as: (1) the occurrence of grade 3 nonhematologic or grade 4 hematologic toxicity (platelets <10 x 109/L, leukocytes <1.0 x 109/L) in two patients at a certain dose level or (2) the occurrence of one grade 4 or two grade 3 nonhematologic toxicities at a certain dose level. If one grade 3 nonhematologic or grade 4 hematologic toxicity occurred at a certain dose level, three additional patients were included at the same dose level before the dose level was raised. Again, clinical follow-up including laboratory parameters and another CT scan were performed 3 months after RIT 2.
HACA Analysis
Serum samples for HACA analysis were drawn before start of the study, after 3 months (before the second diagnostic 131I-cG250 infusion), and after 6 months. The frequency of sampling was increased when patients showed enhanced clearance of the radiolabel from the blood and body as an indicator of HACA formation.
HACA levels in blood samples were assessed retrospectively using ELISA essentially as described previously.6 Results were reported as a number (in nanograms per milliliter NUH-91 equivalents)17 or undetectable. The statistically reliable lower quantification limit of the assay was 40 ng/mL NUH-91. Samples that contained HACA tested positive in two to three independent assay runs.
Pharmacokinetics
Plasma samples to determine the pharmacokinetics of the radiolabeled mAb were drawn up to 7 days after injection of each 131I-cG250 infusion. The clearance rate from plasma was used to detect rapid clearance of radioactivity from the blood and body as a result of immune complex formation induced by HACA, using the clearance rate after the first diagnostic 131I-cG250 infusion as baseline for each patient.
Tumor Responses
Tumor responses were evaluated according to WHO criteria and based on the CT scans read by an independent radiologist. (Complete response, disappearance of all known disease; partial response, at least 50% decrease in the sum of products of largest and perpendicular diameters of measurable lesions without appearance of new lesions or progression of any lesion; stable disease, less than 50% decrease in total tumor size or less than 25% increase in size of one or more measurable lesions; progressive disease, at least 25% increase in size of one or more measurable lesions or appearance of new lesions.) The 6-month follow-up CT was compared with the baseline CT. Responses were reported according to intention to treat.
Statistical Analysis
Statistical analysis of the pharmacokinetic data was performed using Bonferroni corrected, repeated measures, one-way analysis of variance. Differences were considered significant when P < .05, two-sided. All values are expressed as mean ± standard deviation unless stated otherwise.
RESULTS
Radioimmunoscintigraphy
All 29 patients showed sufficient uptake of 131I-cG250 (tumor-to-background ratio, >1.5) in at least one of the known metastatic lesions at 2 to 3 days after injection; ie, no patient was excluded from the protocol.
Skeletal and soft tissue (muscle and [sub]cutaneous) metastases were well visualized (Fig 1A), and additional metastases were frequently delineated in these patients, as shown in Table 2. The newly detected lesions were usually located outside the field of view of the chest/abdomen, but also some small (sub)cutaneous lesions and supraclavicular and axillary lymph node lesions were not noted on the CT (Table 2). Conversely, some metastases visualized on CT were not detected scintigraphically: several lung metastases were not visualized on the scintigraphic images after a diagnostic or high-dose 131I-cG250 infusion (Table 2). In only five of 25 patients with (numerous) pulmonary metastases were lung metastases clearly visualized after the diagnostic 131I-cG250 infusion (Fig 1B). Although the diagnostic 131I-cG250 scans and the post-RIT 131I-cG250 scans were in most cases congruent, in some patients additional metastases were detected on the scans after 131I-cG250 RIT, most frequently in the chest (Table 2). In general, the metastases were better visualized on the images after RIT compared with the diagnostic scintigraphic images.
After the first diagnostic 131I-cG250 injection, two patients (patients 5 and 7) did not receive the first high-dose 131I-cG250 infusion and were not further evaluated because of incomplete data sets (Table 1, Fig 2).
Patient Characteristics, Toxicity, and Clinical Observations
Before study entry, almost all patients had been treated with immunotherapy alone or a combination of immunotherapy and chemotherapy, and some had also received local external beam radiotherapy (Table 1). At inclusion, 12 of 27 (44%) patients were categorized in the intermediate or poor risk groups for survival according to the prognostic factors identified by Motzer et al18 (Table 1). All 131I-cG250 injections were well tolerated by the patients, and no immediate side effects were observed. In addition, the patients who tested retrospectively positive for HACA at the time of a 131I-cG250 injection experienced no acute allergic reactions. In the first weeks after a RIT injection, most patients complained of mild nausea and fatigue.
In all patients, toxicity of the bone marrow was dose limiting. After RIT 1 at a dose level of 2220 MBq (60 mCi)/m2, a drop in platelet and leukocyte counts was observed in all patients, with a nadir between 4 and 6 weeks (Figs 3 and 4). Three patients were considered ineligible for the second RIT because of grade 4 hematologic toxicity in the weeks after RIT 1 (patients 2, 13, and 22) (Table 1, Fig 3). None of the three patients that received RIT 2 of 131I-cG250 at the 1110 MBq (30 mCi)/m2 dose level experienced DLT (Table 1).
Although none of the first three patients treated at the 1,665 MBq (45 mCi)/m2 dose level of RIT 2, experienced DLT, two of three (patients 6 and 12) did show prolonged reduction of platelet and leukocyte counts. Therefore, it was decided to recruit three additional patients at this dose level, one of whom (patient 15) showed a similar pattern. Because three of six patients showed a pronounced drop in platelet counts and a less pronounced drop in leukocyte counts after treatment with RIT 2 at 1665 MBq/m2, which returned to subnormal levels only at 12 weeks after injection, it was decided not to further escalate the dose of RIT 2 to prevent the inherent risk of inducing permanent bone marrow aplasia on a further increase in dose. Thus, the dose level of 2,220 MBq/m2 for RIT 2 was not tested in patients and the MTD of RIT 2 was set at 1,665 MBq/m2. The mean platelet counts of all patients treated with RIT 2 at MTD showed a prolonged platelet drop between 4 and 9 weeks after injection (Fig 3). The drop in mean leukocyte counts after RIT 2 was more gradual (nadir from 7 to 9 weeks after injection) than after RIT 1 and also showed a prolonged time to normalization (Fig 4). In all but one patient, the leukocyte counts eventually normalized, whereas in six of 15 patients, the platelet counts did not reach normal levels within 3 months.
Nineteen of 27 patients received the second high-dose infusion of radiolabeled cG250. Besides grade 4 hematologic toxicities (patients 2, 13, and 22), patients were excluded because of the development of HACA titers (patients 10, 11, and 25) or rapid progressive disease (patients 16 and 26) (Table 1, Fig 2).
Although five patients had elevated serum thyrotropin levels (> 6.0 mU/L), indicating subclinical hypothyroidism at baseline, in only one patient did overt hypothyroidism develop, 10 weeks after RIT 2.
HACA Analysis
Retrospectively, in eight of 27 patients, HACA titers were detectable, ranging from 47 to 57,893 ng/mL NUH-91 equivalents. Patient 10 had (high) HACA titers after RIT 1, as did patients 11 and 25 at the time of the tracer dose before intended RIT 2 and patient 9 at the time RIT 2 was administered, leading to an enhanced clearance of the radiolabel from the blood and body, excluding these patients from the study (Table 1). In the other four patients (patients 1, 14, 21, and 27), the HACA were not clinically relevant, because no enhanced clearance rate of the radiolabel was observed. These patients developed a HACA response relatively late (more than 1 month after a RIT) and/or with relatively low HACA titers. Therefore, in these patients, no enhanced clearance of injected mAb cG250 was detected at the time of RIT injection.
Pharmacokinetics
In patients with negative or low HACA titers, clearance of the radiolabel from the blood after repeated injections of 131I-cG250 was not significantly different from the first injection (P = .77 for t1/2 , P = .35 for t1/2 ?). Half-life of the distribution phase (t1/2 ) was 6.8 ± 2.4 hours, and half-life of the elimination phase (t1/2 ?) was 59.3 ± 9.8 hours. In contrast, rapid clearance of the radiolabel from the blood was noted in patients with highly elevated HACA titers (Fig 5).
Tumor Responses
Four patients were entered in the first phase of the study (treatment of RIT 1 at MTD and treatment of RIT 2 at the first dose level of 1,110 MBq/m2). Of these four patients, two patients remained progressive, one patient showed stabilization of disease during the study, and one patient received only one RIT. In the second phase of the study, patients were entered to receive both RIT treatments at their respective MTDs of 2,220 MBq/m2 and 1,665 MBq/m2. Of the 25 patients in this second cohort, four patients showed stabilization of disease during the study, 12 patients remained progressive, and 11 patients could not adhere to the entire protocol (two patients did not receive RIT 1 and nine patients were treated only with RIT 1). After completion of the study, for the five patients who showed stable disease, stabilization lasted between 3 and 12 months; follow-up CT scans every three months were compared with the baseline study CT scan. None of the eight patients who received only the first RIT (2,220 MBq/m2), and subsequently were excluded from the study for various reasons, were categorized in the favorable risk group at inclusion according to the Motzer criteria.18
DISCUSSION
The first aim of the present study was to determine the safety of two consecutive RIT treatments with 131I-cG250 at MTD in patients with progressive metastasized RCC. Therefore, in the first part of the study, the MTD of the second RIT dose was determined. The second RIT given 12 weeks after RIT 1 could only be escalated to 75% of the MTD of the first RIT because of dose-limiting hematological toxicity, consisting of prolonged recovery times for both platelet and leukocyte counts after RIT 2 compared with RIT 1. This is in contrast to the observations of Behr et al,19 who treated five patients with colorectal cancer with a second RIT of a radioiodinated humanized anticarcinoembryonic antigen antibody at 2220 MBq (60 mCi)/m2, which was the established MTD of the first RIT. In that study, no increased hematological toxicities were observed when the second RIT was given at the same dose level as the first RIT. This could be because the second RIT was given with a greater time interval after the first RIT (8-16 months) than in our study, resulting in a longer recuperating time for the bone marrow.19 However, we could not predict in which patients platelet and/or leukocyte counts did not return to normal values after RIT 2, because platelet and leukocyte counts had returned to pretreatment values after RIT 1 in all patients.
To appreciate hematologic toxicity after RIT, the observations of Blumenthal et al20-22 are of interest. These investigators hypothesize that it is likely that normal platelet or leukocyte counts after myelosuppressive therapy do not reflect accurately the status of the bone marrow. Peripheral-blood cell counts may have normalized, but myelorecovery is still incomplete, reflected by a decrease in pluripotent stem cells. In addition, proliferating stem cells are more radiosensitive than those in the quiescent phase of the cell cycle.22 Thus, a second myelosuppressive therapy while stem cells are actively proliferating may cause enhanced toxicity. This is in line with our observations that in a few patients, platelet and leukocyte counts remained low for a prolonged time and did not return to normal values after RIT 2, suggesting that RIT 2 was given too soon after RIT 1.
In the second part of the study, in which patients were treated with two 131I-cG250 RITs at MTD, HACA was observed in an unexpectedly high number of patients. In eight out of 27 patients, HACA titers could be determined retrospectively. Serum conversions took place within a week after cG250 infusion, but also at later time points, as has been described for the humoral responses to murine immunoglobulins.23-25 In other multiple dosing studies with 131I-cG250,6,7,26 no HACA was observed, most probably because of a difference in protein dosing and/or timing of mAb injections compared with our study, as has been observed for other mAbs.23,25 In patients with accelerated clearance of the radiolabel (four of 27 patients), effective tumor targeting was hampered, thus reducing the therapeutic efficacy of the dose.
The second main aim of the present study was to determine the efficacy of two consecutive RIT treatments with 131I-cG250 at MTD in patients with progressive metastasized RCC. Although no objective responses were observed in this phase II study, five of 29 previously progressive patients stabilized after two 131I-cG250 treatments. We observed no PR, as was reported in one patient in the phase I study.7 Although patients from both studies had stage IV RCC at study entry, almost all patients in the current phase II group had received prior systemic treatment compared with only half of the patients in the phase I study, reflecting a more advanced disease status.7 Our results are more in line with the fractionated 131I-cG250 study, in which also only stable disease was noted.16 Furthermore, the relatively high drop-out rate observed in the current study can solely be attributed to patients categorized in the Motzer prognostic intermediate and poor risk groups. This indicates that patients with a favorable Motzer prognostic risk may be more suitable for treatment with radiolabeled antibodies.
In general, RIT treatments of solid tumors are not as successful as RIT of hematologic malignancies.27-29 In treating solid tumors, more promising results have been observed in patients with small volume disease (eg, in colorectal cancer).19 This can be explained by the higher radiation absorbed dose that can be directed toward smaller tumors. This may be one of the factors responsible for the ineffectiveness of 131I-cG250 in our study, in that most of our patients had bulky disease. Therefore, theoretically, there is room for improvement of RIT with cG250 in patients with RCC by changing the setting to treatment of small-volume disease or in an adjuvant setting. Furthermore, the limited efficacy of cG250 RIT in these patients could be due to the limited range of beta particles of 131I. The long-range beta-emitter 90Y potentially could be a more suitable radionuclide for RIT of the larger tumor lesions in our study than 131I. Furthermore, we demonstrated that the residualizing radionuclides 90Y or 177Lu could potentially deliver higher radiation absorbed doses to RCC tumors than the nonresidualizing radionuclide 131I.30,31 This implies that by changing the radionuclide from 131I to 90Y or 177Lu, cG250-based RIT of RCC can probably be made more effective. In addition, combination radioimmunotherapy with interferon-alfa might be feasible in patients with RCC, because the G250 antigen expression on RCC tumor cells can be upregulated in vitro by IFNs.32
In conclusion, in this phase I/II study of two RIT doses at MTD in patients with progressive stage IV RCC, the MTD of RIT 2 was 75% of the MTD of RIT 1 because of dose-limiting hematological toxicity. Two RITs with 131I-cG250 given 3 months apart were safe and well tolerated in the majority of patients. In these end-stage patients with bulky metastatic disease, no objective responses were observed. HACA developed in eight of 27 patients. This prevented further treatment in four of 27 patients because of accelerated clearance of radiolabeled antibody from the blood. Future RIT studies with monoclonal antibody cG250 should aim at using a residualizing radionuclide such as 177Lu and treatment of small-volume disease or as an adjuvant treatment.
Authors' Disclosures of Potential Conflicts of Interest
Although all authors completed the disclosure declaration, the following authors or their immediate family members indicated a financial interest. No conflict exists for drugs or devices used in a study if they are not being evaluated as part of the investigation. For a detailed description of the disclosure categories, or for more information about ASCO's conflict of interest policy, please refer to the Author Disclosure Declaration and the Disclosures of Potential Conflicts of Interest section in Information for Contributors.
Acknowledgment
We thank Volker Boettger, Wilex AG, Munich, Germany, for performing the ELISA tests to determine the HACA responses. Peter Herzog, radiologist, Munich, Germany, is acknowledged for thoroughly reviewing all CT scans.
NOTES
Supported by Dutch Cancer Society grant No. KUN 99-1973, the Ludwig Institute for Cancer Research, New York, NY, and Wilex AG, München, Germany. E.O. was supported financially by the Ludwig Institute for Cancer Research, New York, NY.
Presented in part at the Society of Nuclear Medicine 2003 meeting in New Orleans, LA, the European Association of Nuclear Medicine 2003 meeting in Amsterdam, The Netherlands and the 10th Conference on Cancer Therapy with Antibodies & Immunoconjugates, Princeton, NJ, October 2004.
Authors' disclosures of potential conflicts of interest are found at the end of this article.
REFERENCES
Greenlee RT, Murray T, Bolden S, et al: Cancer statistics, 2000. CA Cancer J Clin 50:7-33, 2000
Savage PD: Renal cell carcinoma. Curr Opin Oncol 8:247-251, 1996
Yagoda A, Petrylak D, Thompson S: Cytotoxic chemotherapy for advanced renal cell carcinoma. Urol Clin North Am 20:303-321, 1993
Negrier S, Escudier B, Lasset C, et al: Recombinant human interleukin-2, recombinant human interferon alfa-2a, or both in metastatic renal-cell carcinoma. Groupe Francais d'Immunotherapie. N Engl J Med 338:1272-1278, 1998
Fisher RI, Rosenberg SA, Fyfe G: Long-term survival update for high-dose recombinant interleukin-2 in patients with renal cell carcinoma. Cancer J Sci Am 6:S55-S57, 2000 (suppl 1)
Steffens MG, Boerman OC, Oosterwijk-Wakka JC, et al: Targeting of renal cell carcinoma with iodine-131-labeled chimeric monoclonal antibody G250. J Clin Oncol 15:1529-1537, 1997
Steffens MG, Boerman OC, de Mulder PH, et al: Phase I radioimmunotherapy of metastatic renal cell carcinoma with 131I-labeled chimeric monoclonal antibody G250. Clin Cancer Res 5:S3268-S3274, 1999 (suppl 10)
Oosterwijk E, Ruiter DJ, Hoedemaeker PJ, et al: Monoclonal antibody G 250 recognizes a determinant present in renal-cell carcinoma and absent from normal kidney. Int J Cancer 38:489-494, 1986
Pastorek J, Pastorekova S, Callebaut I, et al: Cloning and characterization of MN, a human tumor-associated protein with a domain homologous to carbonic anhydrase and a putative helix- loop-helix DNA binding segment. Oncogene 9:2877-2888, 1994
Opavsky R, Pastorekova S, Zelnik V, et al: Human MN/CA9 gene, a novel member of the carbonic anhydrase family: Structure and exon to protein domain relationships. Genomics 33:480-487, 1996
Grabmaier K, Vissers JL, De Weijert MC, et al: Molecular cloning and immunogenicity of renal cell carcinoma- associated antigen G250. Int J Cancer 85:865-870, 2000
Uemura H, Nakagawa Y, Yoshida K, et al: MN/CA IX/G250 as a potential target for immunotherapy of renal cell carcinomas. Br J Cancer 81:741-746, 1999
Pastorekova S, Parkkila S, Parkkila AK, et al: Carbonic anhydrase IX, MN/CA IX: Analysis of stomach complementary DNA sequence and expression in human and rat alimentary tracts. Gastroenterology 112:398-408, 1997
Steffens MG, Oosterwijk-Wakka JC, Zegwaart-Hagemeier NE, et al: Immunohistochemical analysis of tumor antigen saturation following injection of monoclonal antibody G250. Anticancer Res 19:1197-1200, 1999
Steffens MG, Boerman OC, Oyen WJ, et al: Intratumoral distribution of two consecutive injections of chimeric antibody G250 in primary renal cell carcinoma: Implications for fractionated dose radioimmunotherapy. Cancer Res 59:1615-1619, 1999
Divgi CR, O'Donoghue JA, Welt S, et al: Phase I clinical trial with fractionated radioimmunotherapy using 131I-labeled chimeric G250 in metastatic renal cancer. J Nucl Med 45:1412-1421, 2004
Uemura H, Okajima E, Debruyne FM, et al: Internal image anti-idiotype antibodies related to renal-cell carcinoma- associated antigen G250. Int J Cancer 56:609-614, 1994
Motzer RJ, Mazumdar M, Bacik J, et al: Survival and prognostic stratification of 670 patients with advanced renal cell carcinoma. J Clin Oncol 17:2530-2540, 1999
Behr TM, Liersch T, Greiner-Bechert L, et al: Radioimmunotherapy of small-volume disease of metastatic colorectal cancer. Cancer 94:1373-1381, 2002 (suppl 4)
Blumenthal RD, Lew W, Juweid M, et al: Plasma FLT3-L levels predict bone marrow recovery from myelosuppressive therapy. Cancer 88:333-343, 2000
Siegel JA, Yeldell D, Goldenberg DM, et al: Red marrow radiation dose adjustment using plasma FLT3-L cytokine levels: Improved correlations between hematologic toxicity and bone marrow dose for radioimmunotherapy patients. J Nucl Med 44:67-76, 2003
Juweid ME, Zhang CH, Blumenthal RD, et al: Prediction of hematologic toxicity after radioimmunotherapy with 131I-labeled anticarcinoembryonic antigen monoclonal antibodies. J Nucl Med 40:1609-1616, 1999
Stephens S, Emtage S, Vetterlein O, et al: Comprehensive pharmacokinetics of a humanized antibody and analysis of residual anti-idiotypic responses. Immunology 85:668-674, 1995
Khazaeli MB, Saleh MN, Liu T, et al: Frequent anti-V-region immune response to mouse B72.3 monoclonal antibody. J Clin Immunol 12:116-121, 1992
Gruber R, van Haarlem LJ, Warnaar SO, et al: The human antimouse immunoglobulin response and the anti-idiotypic network have no influence on clinical outcome in patients with minimal residual colorectal cancer treated with monoclonal antibody CO17-1A. Cancer Res 60:1921-1926, 2000
Bleumer I, Knuth A, Oosterwijk E, et al: A phase II trial of chimeric monoclonal antibody G250 for advanced renal cell carcinoma patients. Br J Cancer 90:985-990, 2004
Wiseman GA, White CA, Sparks RB, et al: Biodistribution and dosimetry results from a phase III prospectively randomized controlled trial of Zevalin radioimmunotherapy for low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma. Crit Rev Oncol Hematol 39:181-194, 2001
Goldenberg DM: Targeted therapy of cancer with radiolabeled antibodies. J Nucl Med 43:693-713, 2002
Kaminski MS, Estes J, Zasadny KR, et al: Radioimmunotherapy with iodine (131)I tositumomab for relapsed or refractory B-cell non-Hodgkin lymphoma: Updated results and long-term follow-up of the University of Michigan experience. Blood 96:1259-1266, 2000
Brouwers AH, Buijs WCAM, Oosterwijk E, et al: Targeting of metastatic renal cell carcinoma with the chimeric monoclonal antibody G250 labeled with 131I or 111In: An intrapatient comparison. Clin Cancer Res 9:S3953-S3960, 2003 (suppl)
Brouwers AH, van Eerd JEM, Frielink C, et al: Optimization of radioimmunotherapy of renal cell carcinoma: Labeling of monoclonal antibody cG250 with 131I, 90Y, 177Lu, or 186Re. J Nucl Med 45:327-337, 2004
Brouwers AH, Frielink C, Oosterwijk E, et al: Interferons can upregulate the expression of the tumor associated antigen G250-MN/CA IX, a potential target for (radio)immunotherapy of renal cell carcinoma. Cancer Biother Radiopharm 18:539-548, 2003(Adrienne H. Brouwers, Pet)
Wilex AG, München, Germany
the Department of Radiology, Rijnstate Hospital, Arnhem, The Netherlands
ABSTRACT
PURPOSE: A previous activity dose-escalation study using 131I-labeled chimeric monoclonal antibody cG250 in patients with progressive metastatic renal cell carcinoma (RCC) resulted in occasional therapeutic responses. The present study was designed to determine the safety and therapeutic efficacy of two sequential high-dose treatments with 131I-cG250.
PATIENTS AND METHODS: Patients (n = 29) with progressive metastatic RCC received a low dose of 131I-cG250 for assessment of preferential targeting of metastatic lesions, followed by the first radioimmunotherapy (RIT) with 2220 MBq/m2 131I-cG250 (n = 27) 1 week later. If no grade 4 hematologic toxicity was observed, a second low-dose 131I-cG250 (n = 20) was given 3 months later. When blood clearance was not accelerated, a second RIT of 131I-cG250 was administered at an activity-dose of 1110 MBq/m2 (n = 3) or 1665 MBq/m2 (n = 16). Patients were monitored weekly for toxicity, and tumor size was evaluated by computed tomography once every 3 months intervals.
RESULTS: The maximum-tolerated dose (MTD) of the second RIT was 1,665 MBq/m2 because of dose-limiting hematological toxicity. Based on an intention-to-treat analysis, after two RIT treatments, the disease stabilized in five of 29 patients, whereas it remained progressive in 14 of 29 patients. Two patients received no RIT, and eight of 29 received only one 131I-cG250 RIT because of grade 4 hematologic toxicity, formation of human antichimeric antibodies, or disease progression.
CONCLUSION: In patients with progressive end-stage RCC, the MTD of the second treatment was 75% of the MTD of the first RIT. In the majority of patients, two cycles of 131I-cG250 could be safely administered without severe toxicity. No objective responses were observed, but occasionally two RIT doses resulted in stabilization of previously progressive disease.
INTRODUCTION
With almost 12,000 cancer deaths each year in the United States, renal cell cancer (RCC) accounts for approximately 2% of all cancer deaths.1 Approximately 25% of the patients present with metastatic RCC, and up to half of the patients diagnosed with disease confined to the kidney will ultimately develop metastases.2 Because responses to chemotherapy are poor, there is no role for treatment with chemotherapeutics in these patients.3 Likewise, radiotherapy is only given as palliative treatment of symptomatic metastases. Currently, immunotherapy with interleukin-2 and interferon-alfa, alone or in combination, is the only treatment with curative intent that is available for patients with metastatic RCC, although responses are modest and in the range of 5% to 25%.4,5 Therefore, there is a need for the development of new strategies for the treatment of metastatic RCC.
We aim to develop an effective radioimmunotherapy (RIT) strategy for metastasized RCC using the chimeric monoclonal antibody (mAb) G250 (cG250).6,7 cG250 is a high-affinity (Ka = 4 x 109 M–1), chimeric, immunoglobulin G1 (IgG1) mAb, reactive with the G250 antigen.6,8 The G250 antigen has been identified as carbonic anhydrase isoenzyme 9 (MN/CA IX), a transmembranous glycoprotein.9-11 The antigen is expressed on the cell surface of the majority (> 95%) of clear cell RCCs.12 Approximately 80% of RCCs are of the clear cell type. The reactivity of mAb cG250 to normal human tissues is restricted to the gastrointestinal mucosa and gastrointestinal structures (bile ducts, pancreas).8,13
The chimeric version of the mAb has been developed to reduce its immunogenicity, allowing repeated injections.6 Several clinical studies with 131I-labeled cG250 have been performed. In tumor-targeting studies with radioiodinated cG250 in patients with RCC, Steffens et al14,15 demonstrated that focal uptake of 131I-cG250 in RCC lesions can be extremely high (up to 0.52%ID/g), confirming that potentially high radiation doses can be guided to RCC lesions. In the subsequent phase I activity-dose escalation study, the maximum-tolerated dose (MTD) in patients with metastatic RCC disease was established at 2220 MBq (60 mCi)/m2 131I-cG250.7 In one patient, stable disease was achieved, whereas another patient showed a partial response.7 Divgi et al16 recently reported stable disease in approximately half of the patients treated with fractionated 131I-cG250. However, they did not find evidence for fractionation-induced sparing of the hematopoietic system.16 These studies confirmed the feasibility of repeated dosing of the chimeric version of the antibody.6,7,16
Based on the phase I results,7 a phase I/II study was designed to establish the response rate (phase II) of patients with progressive metastatic RCC treated with high-dose 131I-cG250. The RIT treatment was expanded with an additional RIT treatment to increase the antitumor effect. Because a second RIT of 131I-cG250 had not been given to patients previously, the MTD of the second RIT had to be established first (phase I). Herein, we report the safety and efficacy of two consecutive treatments of 131I-cG250 at MTD in patients with metastatic RCC.
PATIENTS AND METHODS
Patient Characteristics
Twenty-nine patients with clear cell RCC (median age, 57 years; range, 40 to 72 years; 20 men and nine women) were included (Table 1). All patients had undergone a tumor nephrectomy in the past and had measurable progressive disease at the time of enrollment. Participation in the trial was allowed only after at least 6 weeks had passed since the last course of any anti-RCC therapy. Simultaneous treatment with anti-RCC drugs while enrolled onto the study was not permitted, except palliative external beam radiotherapy. Patients had to be older than 18 years of age with a Karnofsky performance status greater than 60. Patients with untreated hypercalcemia, allergic diathesis, significant arrhythmia, complete bundle branch block, electrocardiographic evidence of recent myocardial infarction, life-threatening infection, liver and/or renal failure, fewer than 3.0 x 109 leukocytes/L, fewer than 100 x 109 platelets/L, progressive CNS metastases, or a history of a second malignancy other than treated squamous/basal cell carcinoma of the skin were excluded from the study. In addition, women could not be pregnant or lactating. Patients who dropped out of the study were replaced. The study was closed after 15 patients had completed radiologic and hematologic follow-up 3 months after the second RIT treatment of 131I-cG250 at MTD (estimated size for determining a response rate of 30% [ .05 and ? .20]). The study was approved by the Medical Ethical Committee of the University Medical Center Nijmegen and the institutional review board of the Ludwig Institute for Cancer Research. Before study entry, written informed consent was obtained from all patients.
Monoclonal Antibody cG250 and Radiolabeling
Clinical grade cG250 vials (5 mg/mL) were obtained from The Ludwig Institute for Cancer Research, New York, NY. MAb cG250 was radioiodinated with 131I (MDS Nordion, Fleurus, Belgium) according to the IodoGen method, using a remote system, as described previously.6,7 Diagnostic (tracer) injections consisted of 220 MBq (6 mCi) 131I-cG250 (protein dose, 5 mg). The radioactivity dose of a 131I-cG250 RIT treatment differed for each patient (dosing depending on activity-dose level and body surface area), but the cG250 protein dose remained constant at 5 mg/injection.
Study Design
Within 30 days before study entry, a baseline computed tomography (CT) scan of chest and abdomen was obtained for all patients to adequately monitor the size of metastases. Before the first radioiodinated mAb cG250 administration, evaluation consisted of medical history, physical examination, and blood samples for routine blood chemistry, hematology, and thyroid function. To prevent 131I uptake in the thyroid, patients received potassium iodide and potassium perchlorate. All patients received a diagnostic IV infusion of 131I-cG250 (total volume, 10 mL) followed by acquisition of four whole-body scintigraphic images directly after, 2 to 3, 4 to 5, and 7 days after injection. The images were recorded using a double-headed gamma camera (MultiSpect 2; Siemens Inc, Hoffman Estates, IL), equipped with parallel-hole high-energy collimators (symmetric 15% window over 364 keV; scan speed, 5 cm/min [days 0 and 2/3 after injection] and 4 cm/min [days 4/5 and 7 after injection]) and stored digitally in a 256 x 1,024 matrix. If accumulation of the antibody in metastatic lesions was visualized and the tumor-to-background ratio of at least one of the metastases exceeded 1.5 at day 2 to 3 or 4 to 5 after injection, patients received the first high dose of 131I-cG250 (RIT 1; total volume, 30 to 40 mL) 1 week after administration of the diagnostic dose. The activity dose of RIT 1 of 131I-cG250 was 2,220 MBq (60 mCi)/m2, based on the activity-dose escalation study of Steffens et al.7 Approximately 1 and 2 weeks later, additional whole-body scintigraphic images were recorded (scan speed, 10 cm/min and 4-5 cm/min, respectively). Toxicity was monitored weekly and scored according to the common toxicity criteria (CTC version 2.0) until a definite rise in platelet and leukocyte counts was observed. Clinical follow-up, including laboratory parameters and a repeat CT scan, were performed 12 weeks after the first 131I-cG250 RIT infusion. Irrespective of the outcome of the CT scan evaluation, the same procedure was repeated 3 months after the first RIT treatment unless the patient had experienced grade 4 hematologic toxicity. The second diagnostic infusion (220 MBq/5 mg 131I-cG250) was mainly administered to rule out the presence of human antichimeric antibodies (HACA) that would lead to rapid clearance of the radioiodinated antibody from the blood and body. When this was not observed, patients were treated with a second high dose of 131I-cG250 (RIT 2).
Because there is no experience with a second high-dose injection of 131I-cG250, the MTD of RIT 2 was established first. Before the start of the study, three dose levels were predefined for dose escalation of RIT 2: 1,110 MBq (30 mCi)/m2, 1,655 MBq (45 mCi)/m2, and 2,220 MBq (60 mCi)/m2. Three patients per dose level were entered. If no dose-limiting toxicity (DLT) was observed at a particular dose level, the next three patients were entered at a higher dose level. The MTD was defined as the dose level below the dose at which DLT occurred. If no DLT was observed at the third and highest dose level, MTD would be set at 2220 MBq (60 mCi)/m2. DLT was defined as: (1) the occurrence of grade 3 nonhematologic or grade 4 hematologic toxicity (platelets <10 x 109/L, leukocytes <1.0 x 109/L) in two patients at a certain dose level or (2) the occurrence of one grade 4 or two grade 3 nonhematologic toxicities at a certain dose level. If one grade 3 nonhematologic or grade 4 hematologic toxicity occurred at a certain dose level, three additional patients were included at the same dose level before the dose level was raised. Again, clinical follow-up including laboratory parameters and another CT scan were performed 3 months after RIT 2.
HACA Analysis
Serum samples for HACA analysis were drawn before start of the study, after 3 months (before the second diagnostic 131I-cG250 infusion), and after 6 months. The frequency of sampling was increased when patients showed enhanced clearance of the radiolabel from the blood and body as an indicator of HACA formation.
HACA levels in blood samples were assessed retrospectively using ELISA essentially as described previously.6 Results were reported as a number (in nanograms per milliliter NUH-91 equivalents)17 or undetectable. The statistically reliable lower quantification limit of the assay was 40 ng/mL NUH-91. Samples that contained HACA tested positive in two to three independent assay runs.
Pharmacokinetics
Plasma samples to determine the pharmacokinetics of the radiolabeled mAb were drawn up to 7 days after injection of each 131I-cG250 infusion. The clearance rate from plasma was used to detect rapid clearance of radioactivity from the blood and body as a result of immune complex formation induced by HACA, using the clearance rate after the first diagnostic 131I-cG250 infusion as baseline for each patient.
Tumor Responses
Tumor responses were evaluated according to WHO criteria and based on the CT scans read by an independent radiologist. (Complete response, disappearance of all known disease; partial response, at least 50% decrease in the sum of products of largest and perpendicular diameters of measurable lesions without appearance of new lesions or progression of any lesion; stable disease, less than 50% decrease in total tumor size or less than 25% increase in size of one or more measurable lesions; progressive disease, at least 25% increase in size of one or more measurable lesions or appearance of new lesions.) The 6-month follow-up CT was compared with the baseline CT. Responses were reported according to intention to treat.
Statistical Analysis
Statistical analysis of the pharmacokinetic data was performed using Bonferroni corrected, repeated measures, one-way analysis of variance. Differences were considered significant when P < .05, two-sided. All values are expressed as mean ± standard deviation unless stated otherwise.
RESULTS
Radioimmunoscintigraphy
All 29 patients showed sufficient uptake of 131I-cG250 (tumor-to-background ratio, >1.5) in at least one of the known metastatic lesions at 2 to 3 days after injection; ie, no patient was excluded from the protocol.
Skeletal and soft tissue (muscle and [sub]cutaneous) metastases were well visualized (Fig 1A), and additional metastases were frequently delineated in these patients, as shown in Table 2. The newly detected lesions were usually located outside the field of view of the chest/abdomen, but also some small (sub)cutaneous lesions and supraclavicular and axillary lymph node lesions were not noted on the CT (Table 2). Conversely, some metastases visualized on CT were not detected scintigraphically: several lung metastases were not visualized on the scintigraphic images after a diagnostic or high-dose 131I-cG250 infusion (Table 2). In only five of 25 patients with (numerous) pulmonary metastases were lung metastases clearly visualized after the diagnostic 131I-cG250 infusion (Fig 1B). Although the diagnostic 131I-cG250 scans and the post-RIT 131I-cG250 scans were in most cases congruent, in some patients additional metastases were detected on the scans after 131I-cG250 RIT, most frequently in the chest (Table 2). In general, the metastases were better visualized on the images after RIT compared with the diagnostic scintigraphic images.
After the first diagnostic 131I-cG250 injection, two patients (patients 5 and 7) did not receive the first high-dose 131I-cG250 infusion and were not further evaluated because of incomplete data sets (Table 1, Fig 2).
Patient Characteristics, Toxicity, and Clinical Observations
Before study entry, almost all patients had been treated with immunotherapy alone or a combination of immunotherapy and chemotherapy, and some had also received local external beam radiotherapy (Table 1). At inclusion, 12 of 27 (44%) patients were categorized in the intermediate or poor risk groups for survival according to the prognostic factors identified by Motzer et al18 (Table 1). All 131I-cG250 injections were well tolerated by the patients, and no immediate side effects were observed. In addition, the patients who tested retrospectively positive for HACA at the time of a 131I-cG250 injection experienced no acute allergic reactions. In the first weeks after a RIT injection, most patients complained of mild nausea and fatigue.
In all patients, toxicity of the bone marrow was dose limiting. After RIT 1 at a dose level of 2220 MBq (60 mCi)/m2, a drop in platelet and leukocyte counts was observed in all patients, with a nadir between 4 and 6 weeks (Figs 3 and 4). Three patients were considered ineligible for the second RIT because of grade 4 hematologic toxicity in the weeks after RIT 1 (patients 2, 13, and 22) (Table 1, Fig 3). None of the three patients that received RIT 2 of 131I-cG250 at the 1110 MBq (30 mCi)/m2 dose level experienced DLT (Table 1).
Although none of the first three patients treated at the 1,665 MBq (45 mCi)/m2 dose level of RIT 2, experienced DLT, two of three (patients 6 and 12) did show prolonged reduction of platelet and leukocyte counts. Therefore, it was decided to recruit three additional patients at this dose level, one of whom (patient 15) showed a similar pattern. Because three of six patients showed a pronounced drop in platelet counts and a less pronounced drop in leukocyte counts after treatment with RIT 2 at 1665 MBq/m2, which returned to subnormal levels only at 12 weeks after injection, it was decided not to further escalate the dose of RIT 2 to prevent the inherent risk of inducing permanent bone marrow aplasia on a further increase in dose. Thus, the dose level of 2,220 MBq/m2 for RIT 2 was not tested in patients and the MTD of RIT 2 was set at 1,665 MBq/m2. The mean platelet counts of all patients treated with RIT 2 at MTD showed a prolonged platelet drop between 4 and 9 weeks after injection (Fig 3). The drop in mean leukocyte counts after RIT 2 was more gradual (nadir from 7 to 9 weeks after injection) than after RIT 1 and also showed a prolonged time to normalization (Fig 4). In all but one patient, the leukocyte counts eventually normalized, whereas in six of 15 patients, the platelet counts did not reach normal levels within 3 months.
Nineteen of 27 patients received the second high-dose infusion of radiolabeled cG250. Besides grade 4 hematologic toxicities (patients 2, 13, and 22), patients were excluded because of the development of HACA titers (patients 10, 11, and 25) or rapid progressive disease (patients 16 and 26) (Table 1, Fig 2).
Although five patients had elevated serum thyrotropin levels (> 6.0 mU/L), indicating subclinical hypothyroidism at baseline, in only one patient did overt hypothyroidism develop, 10 weeks after RIT 2.
HACA Analysis
Retrospectively, in eight of 27 patients, HACA titers were detectable, ranging from 47 to 57,893 ng/mL NUH-91 equivalents. Patient 10 had (high) HACA titers after RIT 1, as did patients 11 and 25 at the time of the tracer dose before intended RIT 2 and patient 9 at the time RIT 2 was administered, leading to an enhanced clearance of the radiolabel from the blood and body, excluding these patients from the study (Table 1). In the other four patients (patients 1, 14, 21, and 27), the HACA were not clinically relevant, because no enhanced clearance rate of the radiolabel was observed. These patients developed a HACA response relatively late (more than 1 month after a RIT) and/or with relatively low HACA titers. Therefore, in these patients, no enhanced clearance of injected mAb cG250 was detected at the time of RIT injection.
Pharmacokinetics
In patients with negative or low HACA titers, clearance of the radiolabel from the blood after repeated injections of 131I-cG250 was not significantly different from the first injection (P = .77 for t1/2 , P = .35 for t1/2 ?). Half-life of the distribution phase (t1/2 ) was 6.8 ± 2.4 hours, and half-life of the elimination phase (t1/2 ?) was 59.3 ± 9.8 hours. In contrast, rapid clearance of the radiolabel from the blood was noted in patients with highly elevated HACA titers (Fig 5).
Tumor Responses
Four patients were entered in the first phase of the study (treatment of RIT 1 at MTD and treatment of RIT 2 at the first dose level of 1,110 MBq/m2). Of these four patients, two patients remained progressive, one patient showed stabilization of disease during the study, and one patient received only one RIT. In the second phase of the study, patients were entered to receive both RIT treatments at their respective MTDs of 2,220 MBq/m2 and 1,665 MBq/m2. Of the 25 patients in this second cohort, four patients showed stabilization of disease during the study, 12 patients remained progressive, and 11 patients could not adhere to the entire protocol (two patients did not receive RIT 1 and nine patients were treated only with RIT 1). After completion of the study, for the five patients who showed stable disease, stabilization lasted between 3 and 12 months; follow-up CT scans every three months were compared with the baseline study CT scan. None of the eight patients who received only the first RIT (2,220 MBq/m2), and subsequently were excluded from the study for various reasons, were categorized in the favorable risk group at inclusion according to the Motzer criteria.18
DISCUSSION
The first aim of the present study was to determine the safety of two consecutive RIT treatments with 131I-cG250 at MTD in patients with progressive metastasized RCC. Therefore, in the first part of the study, the MTD of the second RIT dose was determined. The second RIT given 12 weeks after RIT 1 could only be escalated to 75% of the MTD of the first RIT because of dose-limiting hematological toxicity, consisting of prolonged recovery times for both platelet and leukocyte counts after RIT 2 compared with RIT 1. This is in contrast to the observations of Behr et al,19 who treated five patients with colorectal cancer with a second RIT of a radioiodinated humanized anticarcinoembryonic antigen antibody at 2220 MBq (60 mCi)/m2, which was the established MTD of the first RIT. In that study, no increased hematological toxicities were observed when the second RIT was given at the same dose level as the first RIT. This could be because the second RIT was given with a greater time interval after the first RIT (8-16 months) than in our study, resulting in a longer recuperating time for the bone marrow.19 However, we could not predict in which patients platelet and/or leukocyte counts did not return to normal values after RIT 2, because platelet and leukocyte counts had returned to pretreatment values after RIT 1 in all patients.
To appreciate hematologic toxicity after RIT, the observations of Blumenthal et al20-22 are of interest. These investigators hypothesize that it is likely that normal platelet or leukocyte counts after myelosuppressive therapy do not reflect accurately the status of the bone marrow. Peripheral-blood cell counts may have normalized, but myelorecovery is still incomplete, reflected by a decrease in pluripotent stem cells. In addition, proliferating stem cells are more radiosensitive than those in the quiescent phase of the cell cycle.22 Thus, a second myelosuppressive therapy while stem cells are actively proliferating may cause enhanced toxicity. This is in line with our observations that in a few patients, platelet and leukocyte counts remained low for a prolonged time and did not return to normal values after RIT 2, suggesting that RIT 2 was given too soon after RIT 1.
In the second part of the study, in which patients were treated with two 131I-cG250 RITs at MTD, HACA was observed in an unexpectedly high number of patients. In eight out of 27 patients, HACA titers could be determined retrospectively. Serum conversions took place within a week after cG250 infusion, but also at later time points, as has been described for the humoral responses to murine immunoglobulins.23-25 In other multiple dosing studies with 131I-cG250,6,7,26 no HACA was observed, most probably because of a difference in protein dosing and/or timing of mAb injections compared with our study, as has been observed for other mAbs.23,25 In patients with accelerated clearance of the radiolabel (four of 27 patients), effective tumor targeting was hampered, thus reducing the therapeutic efficacy of the dose.
The second main aim of the present study was to determine the efficacy of two consecutive RIT treatments with 131I-cG250 at MTD in patients with progressive metastasized RCC. Although no objective responses were observed in this phase II study, five of 29 previously progressive patients stabilized after two 131I-cG250 treatments. We observed no PR, as was reported in one patient in the phase I study.7 Although patients from both studies had stage IV RCC at study entry, almost all patients in the current phase II group had received prior systemic treatment compared with only half of the patients in the phase I study, reflecting a more advanced disease status.7 Our results are more in line with the fractionated 131I-cG250 study, in which also only stable disease was noted.16 Furthermore, the relatively high drop-out rate observed in the current study can solely be attributed to patients categorized in the Motzer prognostic intermediate and poor risk groups. This indicates that patients with a favorable Motzer prognostic risk may be more suitable for treatment with radiolabeled antibodies.
In general, RIT treatments of solid tumors are not as successful as RIT of hematologic malignancies.27-29 In treating solid tumors, more promising results have been observed in patients with small volume disease (eg, in colorectal cancer).19 This can be explained by the higher radiation absorbed dose that can be directed toward smaller tumors. This may be one of the factors responsible for the ineffectiveness of 131I-cG250 in our study, in that most of our patients had bulky disease. Therefore, theoretically, there is room for improvement of RIT with cG250 in patients with RCC by changing the setting to treatment of small-volume disease or in an adjuvant setting. Furthermore, the limited efficacy of cG250 RIT in these patients could be due to the limited range of beta particles of 131I. The long-range beta-emitter 90Y potentially could be a more suitable radionuclide for RIT of the larger tumor lesions in our study than 131I. Furthermore, we demonstrated that the residualizing radionuclides 90Y or 177Lu could potentially deliver higher radiation absorbed doses to RCC tumors than the nonresidualizing radionuclide 131I.30,31 This implies that by changing the radionuclide from 131I to 90Y or 177Lu, cG250-based RIT of RCC can probably be made more effective. In addition, combination radioimmunotherapy with interferon-alfa might be feasible in patients with RCC, because the G250 antigen expression on RCC tumor cells can be upregulated in vitro by IFNs.32
In conclusion, in this phase I/II study of two RIT doses at MTD in patients with progressive stage IV RCC, the MTD of RIT 2 was 75% of the MTD of RIT 1 because of dose-limiting hematological toxicity. Two RITs with 131I-cG250 given 3 months apart were safe and well tolerated in the majority of patients. In these end-stage patients with bulky metastatic disease, no objective responses were observed. HACA developed in eight of 27 patients. This prevented further treatment in four of 27 patients because of accelerated clearance of radiolabeled antibody from the blood. Future RIT studies with monoclonal antibody cG250 should aim at using a residualizing radionuclide such as 177Lu and treatment of small-volume disease or as an adjuvant treatment.
Authors' Disclosures of Potential Conflicts of Interest
Although all authors completed the disclosure declaration, the following authors or their immediate family members indicated a financial interest. No conflict exists for drugs or devices used in a study if they are not being evaluated as part of the investigation. For a detailed description of the disclosure categories, or for more information about ASCO's conflict of interest policy, please refer to the Author Disclosure Declaration and the Disclosures of Potential Conflicts of Interest section in Information for Contributors.
Acknowledgment
We thank Volker Boettger, Wilex AG, Munich, Germany, for performing the ELISA tests to determine the HACA responses. Peter Herzog, radiologist, Munich, Germany, is acknowledged for thoroughly reviewing all CT scans.
NOTES
Supported by Dutch Cancer Society grant No. KUN 99-1973, the Ludwig Institute for Cancer Research, New York, NY, and Wilex AG, München, Germany. E.O. was supported financially by the Ludwig Institute for Cancer Research, New York, NY.
Presented in part at the Society of Nuclear Medicine 2003 meeting in New Orleans, LA, the European Association of Nuclear Medicine 2003 meeting in Amsterdam, The Netherlands and the 10th Conference on Cancer Therapy with Antibodies & Immunoconjugates, Princeton, NJ, October 2004.
Authors' disclosures of potential conflicts of interest are found at the end of this article.
REFERENCES
Greenlee RT, Murray T, Bolden S, et al: Cancer statistics, 2000. CA Cancer J Clin 50:7-33, 2000
Savage PD: Renal cell carcinoma. Curr Opin Oncol 8:247-251, 1996
Yagoda A, Petrylak D, Thompson S: Cytotoxic chemotherapy for advanced renal cell carcinoma. Urol Clin North Am 20:303-321, 1993
Negrier S, Escudier B, Lasset C, et al: Recombinant human interleukin-2, recombinant human interferon alfa-2a, or both in metastatic renal-cell carcinoma. Groupe Francais d'Immunotherapie. N Engl J Med 338:1272-1278, 1998
Fisher RI, Rosenberg SA, Fyfe G: Long-term survival update for high-dose recombinant interleukin-2 in patients with renal cell carcinoma. Cancer J Sci Am 6:S55-S57, 2000 (suppl 1)
Steffens MG, Boerman OC, Oosterwijk-Wakka JC, et al: Targeting of renal cell carcinoma with iodine-131-labeled chimeric monoclonal antibody G250. J Clin Oncol 15:1529-1537, 1997
Steffens MG, Boerman OC, de Mulder PH, et al: Phase I radioimmunotherapy of metastatic renal cell carcinoma with 131I-labeled chimeric monoclonal antibody G250. Clin Cancer Res 5:S3268-S3274, 1999 (suppl 10)
Oosterwijk E, Ruiter DJ, Hoedemaeker PJ, et al: Monoclonal antibody G 250 recognizes a determinant present in renal-cell carcinoma and absent from normal kidney. Int J Cancer 38:489-494, 1986
Pastorek J, Pastorekova S, Callebaut I, et al: Cloning and characterization of MN, a human tumor-associated protein with a domain homologous to carbonic anhydrase and a putative helix- loop-helix DNA binding segment. Oncogene 9:2877-2888, 1994
Opavsky R, Pastorekova S, Zelnik V, et al: Human MN/CA9 gene, a novel member of the carbonic anhydrase family: Structure and exon to protein domain relationships. Genomics 33:480-487, 1996
Grabmaier K, Vissers JL, De Weijert MC, et al: Molecular cloning and immunogenicity of renal cell carcinoma- associated antigen G250. Int J Cancer 85:865-870, 2000
Uemura H, Nakagawa Y, Yoshida K, et al: MN/CA IX/G250 as a potential target for immunotherapy of renal cell carcinomas. Br J Cancer 81:741-746, 1999
Pastorekova S, Parkkila S, Parkkila AK, et al: Carbonic anhydrase IX, MN/CA IX: Analysis of stomach complementary DNA sequence and expression in human and rat alimentary tracts. Gastroenterology 112:398-408, 1997
Steffens MG, Oosterwijk-Wakka JC, Zegwaart-Hagemeier NE, et al: Immunohistochemical analysis of tumor antigen saturation following injection of monoclonal antibody G250. Anticancer Res 19:1197-1200, 1999
Steffens MG, Boerman OC, Oyen WJ, et al: Intratumoral distribution of two consecutive injections of chimeric antibody G250 in primary renal cell carcinoma: Implications for fractionated dose radioimmunotherapy. Cancer Res 59:1615-1619, 1999
Divgi CR, O'Donoghue JA, Welt S, et al: Phase I clinical trial with fractionated radioimmunotherapy using 131I-labeled chimeric G250 in metastatic renal cancer. J Nucl Med 45:1412-1421, 2004
Uemura H, Okajima E, Debruyne FM, et al: Internal image anti-idiotype antibodies related to renal-cell carcinoma- associated antigen G250. Int J Cancer 56:609-614, 1994
Motzer RJ, Mazumdar M, Bacik J, et al: Survival and prognostic stratification of 670 patients with advanced renal cell carcinoma. J Clin Oncol 17:2530-2540, 1999
Behr TM, Liersch T, Greiner-Bechert L, et al: Radioimmunotherapy of small-volume disease of metastatic colorectal cancer. Cancer 94:1373-1381, 2002 (suppl 4)
Blumenthal RD, Lew W, Juweid M, et al: Plasma FLT3-L levels predict bone marrow recovery from myelosuppressive therapy. Cancer 88:333-343, 2000
Siegel JA, Yeldell D, Goldenberg DM, et al: Red marrow radiation dose adjustment using plasma FLT3-L cytokine levels: Improved correlations between hematologic toxicity and bone marrow dose for radioimmunotherapy patients. J Nucl Med 44:67-76, 2003
Juweid ME, Zhang CH, Blumenthal RD, et al: Prediction of hematologic toxicity after radioimmunotherapy with 131I-labeled anticarcinoembryonic antigen monoclonal antibodies. J Nucl Med 40:1609-1616, 1999
Stephens S, Emtage S, Vetterlein O, et al: Comprehensive pharmacokinetics of a humanized antibody and analysis of residual anti-idiotypic responses. Immunology 85:668-674, 1995
Khazaeli MB, Saleh MN, Liu T, et al: Frequent anti-V-region immune response to mouse B72.3 monoclonal antibody. J Clin Immunol 12:116-121, 1992
Gruber R, van Haarlem LJ, Warnaar SO, et al: The human antimouse immunoglobulin response and the anti-idiotypic network have no influence on clinical outcome in patients with minimal residual colorectal cancer treated with monoclonal antibody CO17-1A. Cancer Res 60:1921-1926, 2000
Bleumer I, Knuth A, Oosterwijk E, et al: A phase II trial of chimeric monoclonal antibody G250 for advanced renal cell carcinoma patients. Br J Cancer 90:985-990, 2004
Wiseman GA, White CA, Sparks RB, et al: Biodistribution and dosimetry results from a phase III prospectively randomized controlled trial of Zevalin radioimmunotherapy for low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma. Crit Rev Oncol Hematol 39:181-194, 2001
Goldenberg DM: Targeted therapy of cancer with radiolabeled antibodies. J Nucl Med 43:693-713, 2002
Kaminski MS, Estes J, Zasadny KR, et al: Radioimmunotherapy with iodine (131)I tositumomab for relapsed or refractory B-cell non-Hodgkin lymphoma: Updated results and long-term follow-up of the University of Michigan experience. Blood 96:1259-1266, 2000
Brouwers AH, Buijs WCAM, Oosterwijk E, et al: Targeting of metastatic renal cell carcinoma with the chimeric monoclonal antibody G250 labeled with 131I or 111In: An intrapatient comparison. Clin Cancer Res 9:S3953-S3960, 2003 (suppl)
Brouwers AH, van Eerd JEM, Frielink C, et al: Optimization of radioimmunotherapy of renal cell carcinoma: Labeling of monoclonal antibody cG250 with 131I, 90Y, 177Lu, or 186Re. J Nucl Med 45:327-337, 2004
Brouwers AH, Frielink C, Oosterwijk E, et al: Interferons can upregulate the expression of the tumor associated antigen G250-MN/CA IX, a potential target for (radio)immunotherapy of renal cell carcinoma. Cancer Biother Radiopharm 18:539-548, 2003(Adrienne H. Brouwers, Pet)