Presentation on websites of possible benefits and harms from screening for breast cancer: cross sectional study
http://www.100md.com
《英国医生杂志》
1 Nordic Cochrane Centre, H:S Rigshospitalet, DK-2100 K?benhavn ?, Denmark
Correspondence to: Peter C G?tzsche pcg@cochrane.dk
Abstract
Women can get information about the possible benefits and harms of mammographic screening from governmental institutions and professional advocacy groups. This information could be biased, however, since the success of a screening programme depends on the participation rate. Another potential conflict of interest is industry funding of advocacy groups.
A review of 58 Australian pamphlets in 1998 showed that the information presented to women invited for breast cancer screening was biased and insufficient and did not allow fully informed consent.1 Another Australian study, of 54 publications used to inform about screening mammography in New South Wales, showed that only 18% of the publications gave any information on false positive and false negative results, and only 48% gave any information on adverse effects.2
In the European Union an average of 23% of the population use the internet to find information about health issues; Denmark has the highest rate, at 47%.3 If the information about screening on the internet is biased, women's status as autonomous individuals could be violated.4 The importance of balanced information is underlined by a study which found that 61% of women decided for themselves whether to have a screening mammogram, and a further 26% made the decision together with their doctor.5
In 2001 the quality of the randomised trials of mammographic screening was criticised in a comprehensive Cochrane review that questioned the benefit of screening.6 In addition, important harms related to overdiagnosis and overtreatment were demonstrated.7 8 We therefore decided to study whether the current information on the internet was balanced and reflected the recent findings.
Materials and methods
Recommendations on websites
We located 27 websites, 13 from professional advocacy groups, 11 from governmental institutions, and three from consumer organisations (see appendix on bmj.com). The governmental and advocacy sites all recommended mammography screening, at least implicitly, whereas the consumer sites questioned the value of screening (P = 0.0007).
Funding
All 13 advocacy groups accepted sponsorship from industry, apparently without restrictions. The Canadian Cancer Society noted that "Partnership with the Canadian Cancer Society can assist your company in reaching your commercial objectives." In contrast, the three consumer organisations explicitly acknowledged the risk of bias related to industry funding: two (Breast Cancer Action and Center for Medical Consumers) said that they did not accept grants from industry, while the third (National Breast Cancer Coalition) noted that only 15% of its budget can come from corporations, only 5% from any single source, and that this funding is restricted to general operating support.
Information items
The sites had a median of three information items out of the 17 possible; the highest number was 13 (Center for Medical Consumers). Five sites had none, and these sites mainly addressed practical issues related to the examination. The median number of items was nine for the three consumer sites, which were sceptical about screening, and three for the other sites (P = 0.03). Our two independent assessments of the sites identified a total of 98 and 99 information items; after discussion, we agreed on 118 items. The discrepancies were mainly caused by oversight. The significant difference between the consumer sites and the other sites persisted for the individual assessments (P = 0.03).
The four most common information items were the same as in the 1998 study of pamphlets (table 1), but more websites described the relative and absolute risk reduction of death from breast cancer (P = 0.006 and P = 0.005, respectively), the proportion of women recalled (P = 0.006), and the predictive value of a positive mammogram (P = 0.02). The relative risk reduction was usually given as 30%, but estimates varied from none to 50% reduction. Three times as many sites provided the relative risk reduction as provided the absolute risk reduction (table 1).
Table 1 Presence of information items about screening for breast cancer on 27 websites (from professional advocacy groups, governmental institutions, and consumer organisations) and in a 1998 survey of 58 pamphlets1
For the seven new items we added to those used in the survey of pamphlets, information was rarely provided on relative risk reduction of total mortality (only two sites did so) and risks related to radiotherapy (four sites). Information on the other items was provided by a quarter to half of the websites (table 1). The three consumer sites mentioned overdiagnosis and overtreatment, but only four of the other 24 sites did so (P = 0.02).
Bias in selection and presentation of information
The essence of the messages varied widely (see box). Most websites omitted information on important harms (table 1) and emphasised possible benefits in a way that would be expected to increase uptake of screening. For example, 12 sites mentioned lifetime risk of developing breast cancer, usually followed by the annual number of diagnoses. In contrast, only three sites mentioned the relatively reassuring message that women have a more than 50% chance of surviving breast cancer once it is diagnosed, and only four stated that the lifetime risk of dying from breast cancer is about 3-4% (depending on country). Twelve sites stated the number of women recalled and presented this as about 5% at each screening round.
Issues related to carcinoma in situ, overdiagnosis and overtreatment, and number and type of operations were mentioned by a quarter to a third of the sites (table 1), but often in a misleading or erroneous fashion (see box). Four governmental websites and one advocacy site indicated that screening leads to fewer mastectomies. One governmental and three advocacy sites noted that it is beneficial to detect and remove carcinoma in situ since it would then not recur. Only two such sites mentioned that screening can detect cancers that may never progress, compared with all three consumer sites (P = 0.007). Only four sites noted that there could be risks associated with radiotherapy, but the risks were downgraded on three of the sites (see box).
The three consumer sites described psychological distress related to false positive findings, compared with seven of the governmental or advocacy sites (P = 0.08); seven sites described it vaguely as "anxiety," and no sites gave an estimate of the incidence. The potential pain inflicted by the mammographic procedure was mentioned by 14 sites, three of which claimed that the procedure shouldn't be painful.
Discussion
Slaytor EK, Ward JE. How risks of breast cancer and the benefits of screening are communicated to women: analysis of 58 pamphlets. BMJ 1998;317: 263-4.
Croft E, Barratt A, Butow P. Information about tests for breast cancer: what are we telling people? J Fam Pract 2002;51: 858-60.
European Opinion Research Group. European Union citizens and sources of information about health. 2003. http://europa.eu.int/comm/health/ph_information/documents/eb_58_en.pdf (accessed 3 Oct 2003).
Raffle AE. Information about screening—is it to achieve high uptake or to ensure informed choice? Health Expect 2001;4: 92-6.
Davey HM, Barratt AL, Davey E, Butow PN, Redman S, Houssami N, et al. Medical tests: women's reported and preferred decision-making roles and preferences for information on benefits, side-effects and false results. Health Expect 2002;5: 330-40.
Olsen O, G?tzsche PC. Screening for breast cancer with mammography. Cochrane Database Syst Rev 2001;(4): CD001877 .
Olsen O, G?tzsche PC. Cochrane review on screening for breast cancer with mammography. Lancet 2001;358: 1340-2.
Olsen O, G?tzsche PC. Systematic review of screening for breast cancer with mammography. 2001. http://image.thelancet.com/lancet/extra/fullreport.pdf (accessed 8 Jan 2004).
Screening—en redeg?relse. K?benhavn: Det Etiske R?d; 1999.
Elmore JG, Barton MB, Moceri VM, Polk S, Arena PJ, Fletcher SW. Ten-year risk of false positive screening mammograms and clinical breast examinations. N Engl J Med 1998;338: 1089-96.
Early Breast Cancer Trialists' Collaborative Group. Favourable and unfavourable effects on long-term survival of radiotherapy for early breast cancer: an overview of the randomised trials. Lancet 2000;355: 1757-70.
General Medical Council. Seeking patients' consent: the ethical considerations. London: General Medical Council, 1998. www.gmc-uk.org/standards/consent.htm (accessed 8 Jan 2004).
Wolf AM, Nasser JF, Wolf AM, Schorling JB. The impact of informed consent on patient interest in prostate-specific antigen screening. Arch Intern Med 1996;156: 1333-6.
Ransohoff DF, Harris R. Lessons from the mammography screening controversy: can we improve the debate? Ann Intern Med 1997;127: 1029-34.
Naylor D. Measured enthusiasm: does the method of reporting trial results alter perceptions of therapeutic effectiveness. Ann Intern Med 1992;117: 916-21.
Nystr?m L, Rutqvist LE, Wall S, Lindgren A, Lindqvist M, Ryden S, et al. Breast cancer screening with mammography: overview of Swedish randomised trials. Lancet 1993;341: 973-8.
Tidlig opsporing og behandling af brystkr?ft: statusrapport. K?benhavn: Sundhedsstyrelsen, 1997.
Early Breast Cancer Trialists' Collaborative Group. Effects of radiotherapy and surgery in early breast cancer: an overview of the randomized trials. N Engl J Med 1995;333: 1444-55.
G?tzsche PC. Update on effects of screening mammography. Lancet 2002;360: 338.
Nystr?m L, Andersson I, Bjurstam N, Frisell J, Rutqvist LE. Update on effects of screening mammography: authors' reply . Lancet 2002;360: 339-40.
G?tzsche PC. Screening for breast cancer with mammography: author's reply. Lancet 2001;358: 2167-8.
Miller AB. The costs and benefits of breast cancer screening. Am J Prev Med 1993;9: 175-80.
Andersson I, Aspegren K, Janzon L, Landberg T, Lindholm K, Linell F, et al. Mammographic screening and mortality from breast cancer: the Malmo mammographic screening trial. BMJ 1988;297: 943-8.
G?tzsche PC. On the benefits and harms of screening for breast cancer. Int J Epidemiol (in press).
Ries LAG, Eisner MP, Kosary CL, Hankey BF, Miller BA, Clegg L, et al, eds. SEER cancer statistics review, 1973-1999. Bethesda, MD: National Cancer Institute, 2002. (http://seer.cancer.gov/csr/1973_1999/).
Douek M, Baum M. Mass breast screening: is there a hidden cost? Br J Surg 2003;90(suppl 1):June (Abstract Breast 14).
McNoe B, Miller D, Elwood M. Women's experience of the Otago-Southland breast screening programme—a compilation of five studies. Dunedin: Hugh Adam Cancer Epidemiology Unit, 1996.
Elwood M, McNoe B, Smith T, Bandaranayake M, Doyle TC. Once is enough—why some women do not continue to participate in a breast cancer screening programme. N Z Med J 1998;111: 180-3.
Bekelman JE, Li Y, Gross CP. Scope and impact of financial conflicts of interest in biomedical research: a systematic review. JAMA 2003;289; 454-65.
Lexchin J, Bero LA, Djulbegovic B, Clark O. Pharmaceutical industry sponsorship and research outcome and quality: systematic review. BMJ 2003;326: 1167-70.
G?tzsche PC. Office of NHS cancer screening programme misrepresents Nordic work in breast screening row. BMJ 2001;323: 1131.
Schwartz LM, Woloshin S, Sox HC, Fischhoff B, Welch HG. US women's attitudes to false positive mammography results and detection of ductal carcinoma in situ: cross sectional survey. BMJ 2000;320: 1635-40.
Mateau TM. A measure of informed choice. Health Expect 2001;4: 99-108.
NHS. Breast screening, the facts. London: Health Promotion England, 2001. www.cancerscreening.nhs.uk/breastscreen/publications/ia-02.html (accessed 8 Jan 2004).
Horton R. Screening mammography: setting the record straight. Lancet 2002;359: 441-2.
Nystr?m L, Larsson LG, Wall S, Rutqvist LE, Andersson I, Bjurstam N, et al. An overview of the Swedish randomised mammography trials: total mortality pattern and the representivity of the study cohorts. J Med Screen 1996;3: 85-7.
Thornton H. Consequences of breast screening. Lancet 2000;356: 1033.
US Preventive Services Task Force. Screening for breast cancer: recommendations and rationale. Ann Intern Med 2002;137: 344-6.(Karsten Juhl J?rgensen, p)
Correspondence to: Peter C G?tzsche pcg@cochrane.dk
Abstract
Women can get information about the possible benefits and harms of mammographic screening from governmental institutions and professional advocacy groups. This information could be biased, however, since the success of a screening programme depends on the participation rate. Another potential conflict of interest is industry funding of advocacy groups.
A review of 58 Australian pamphlets in 1998 showed that the information presented to women invited for breast cancer screening was biased and insufficient and did not allow fully informed consent.1 Another Australian study, of 54 publications used to inform about screening mammography in New South Wales, showed that only 18% of the publications gave any information on false positive and false negative results, and only 48% gave any information on adverse effects.2
In the European Union an average of 23% of the population use the internet to find information about health issues; Denmark has the highest rate, at 47%.3 If the information about screening on the internet is biased, women's status as autonomous individuals could be violated.4 The importance of balanced information is underlined by a study which found that 61% of women decided for themselves whether to have a screening mammogram, and a further 26% made the decision together with their doctor.5
In 2001 the quality of the randomised trials of mammographic screening was criticised in a comprehensive Cochrane review that questioned the benefit of screening.6 In addition, important harms related to overdiagnosis and overtreatment were demonstrated.7 8 We therefore decided to study whether the current information on the internet was balanced and reflected the recent findings.
Materials and methods
Recommendations on websites
We located 27 websites, 13 from professional advocacy groups, 11 from governmental institutions, and three from consumer organisations (see appendix on bmj.com). The governmental and advocacy sites all recommended mammography screening, at least implicitly, whereas the consumer sites questioned the value of screening (P = 0.0007).
Funding
All 13 advocacy groups accepted sponsorship from industry, apparently without restrictions. The Canadian Cancer Society noted that "Partnership with the Canadian Cancer Society can assist your company in reaching your commercial objectives." In contrast, the three consumer organisations explicitly acknowledged the risk of bias related to industry funding: two (Breast Cancer Action and Center for Medical Consumers) said that they did not accept grants from industry, while the third (National Breast Cancer Coalition) noted that only 15% of its budget can come from corporations, only 5% from any single source, and that this funding is restricted to general operating support.
Information items
The sites had a median of three information items out of the 17 possible; the highest number was 13 (Center for Medical Consumers). Five sites had none, and these sites mainly addressed practical issues related to the examination. The median number of items was nine for the three consumer sites, which were sceptical about screening, and three for the other sites (P = 0.03). Our two independent assessments of the sites identified a total of 98 and 99 information items; after discussion, we agreed on 118 items. The discrepancies were mainly caused by oversight. The significant difference between the consumer sites and the other sites persisted for the individual assessments (P = 0.03).
The four most common information items were the same as in the 1998 study of pamphlets (table 1), but more websites described the relative and absolute risk reduction of death from breast cancer (P = 0.006 and P = 0.005, respectively), the proportion of women recalled (P = 0.006), and the predictive value of a positive mammogram (P = 0.02). The relative risk reduction was usually given as 30%, but estimates varied from none to 50% reduction. Three times as many sites provided the relative risk reduction as provided the absolute risk reduction (table 1).
Table 1 Presence of information items about screening for breast cancer on 27 websites (from professional advocacy groups, governmental institutions, and consumer organisations) and in a 1998 survey of 58 pamphlets1
For the seven new items we added to those used in the survey of pamphlets, information was rarely provided on relative risk reduction of total mortality (only two sites did so) and risks related to radiotherapy (four sites). Information on the other items was provided by a quarter to half of the websites (table 1). The three consumer sites mentioned overdiagnosis and overtreatment, but only four of the other 24 sites did so (P = 0.02).
Bias in selection and presentation of information
The essence of the messages varied widely (see box). Most websites omitted information on important harms (table 1) and emphasised possible benefits in a way that would be expected to increase uptake of screening. For example, 12 sites mentioned lifetime risk of developing breast cancer, usually followed by the annual number of diagnoses. In contrast, only three sites mentioned the relatively reassuring message that women have a more than 50% chance of surviving breast cancer once it is diagnosed, and only four stated that the lifetime risk of dying from breast cancer is about 3-4% (depending on country). Twelve sites stated the number of women recalled and presented this as about 5% at each screening round.
Issues related to carcinoma in situ, overdiagnosis and overtreatment, and number and type of operations were mentioned by a quarter to a third of the sites (table 1), but often in a misleading or erroneous fashion (see box). Four governmental websites and one advocacy site indicated that screening leads to fewer mastectomies. One governmental and three advocacy sites noted that it is beneficial to detect and remove carcinoma in situ since it would then not recur. Only two such sites mentioned that screening can detect cancers that may never progress, compared with all three consumer sites (P = 0.007). Only four sites noted that there could be risks associated with radiotherapy, but the risks were downgraded on three of the sites (see box).
The three consumer sites described psychological distress related to false positive findings, compared with seven of the governmental or advocacy sites (P = 0.08); seven sites described it vaguely as "anxiety," and no sites gave an estimate of the incidence. The potential pain inflicted by the mammographic procedure was mentioned by 14 sites, three of which claimed that the procedure shouldn't be painful.
Discussion
Slaytor EK, Ward JE. How risks of breast cancer and the benefits of screening are communicated to women: analysis of 58 pamphlets. BMJ 1998;317: 263-4.
Croft E, Barratt A, Butow P. Information about tests for breast cancer: what are we telling people? J Fam Pract 2002;51: 858-60.
European Opinion Research Group. European Union citizens and sources of information about health. 2003. http://europa.eu.int/comm/health/ph_information/documents/eb_58_en.pdf (accessed 3 Oct 2003).
Raffle AE. Information about screening—is it to achieve high uptake or to ensure informed choice? Health Expect 2001;4: 92-6.
Davey HM, Barratt AL, Davey E, Butow PN, Redman S, Houssami N, et al. Medical tests: women's reported and preferred decision-making roles and preferences for information on benefits, side-effects and false results. Health Expect 2002;5: 330-40.
Olsen O, G?tzsche PC. Screening for breast cancer with mammography. Cochrane Database Syst Rev 2001;(4): CD001877 .
Olsen O, G?tzsche PC. Cochrane review on screening for breast cancer with mammography. Lancet 2001;358: 1340-2.
Olsen O, G?tzsche PC. Systematic review of screening for breast cancer with mammography. 2001. http://image.thelancet.com/lancet/extra/fullreport.pdf (accessed 8 Jan 2004).
Screening—en redeg?relse. K?benhavn: Det Etiske R?d; 1999.
Elmore JG, Barton MB, Moceri VM, Polk S, Arena PJ, Fletcher SW. Ten-year risk of false positive screening mammograms and clinical breast examinations. N Engl J Med 1998;338: 1089-96.
Early Breast Cancer Trialists' Collaborative Group. Favourable and unfavourable effects on long-term survival of radiotherapy for early breast cancer: an overview of the randomised trials. Lancet 2000;355: 1757-70.
General Medical Council. Seeking patients' consent: the ethical considerations. London: General Medical Council, 1998. www.gmc-uk.org/standards/consent.htm (accessed 8 Jan 2004).
Wolf AM, Nasser JF, Wolf AM, Schorling JB. The impact of informed consent on patient interest in prostate-specific antigen screening. Arch Intern Med 1996;156: 1333-6.
Ransohoff DF, Harris R. Lessons from the mammography screening controversy: can we improve the debate? Ann Intern Med 1997;127: 1029-34.
Naylor D. Measured enthusiasm: does the method of reporting trial results alter perceptions of therapeutic effectiveness. Ann Intern Med 1992;117: 916-21.
Nystr?m L, Rutqvist LE, Wall S, Lindgren A, Lindqvist M, Ryden S, et al. Breast cancer screening with mammography: overview of Swedish randomised trials. Lancet 1993;341: 973-8.
Tidlig opsporing og behandling af brystkr?ft: statusrapport. K?benhavn: Sundhedsstyrelsen, 1997.
Early Breast Cancer Trialists' Collaborative Group. Effects of radiotherapy and surgery in early breast cancer: an overview of the randomized trials. N Engl J Med 1995;333: 1444-55.
G?tzsche PC. Update on effects of screening mammography. Lancet 2002;360: 338.
Nystr?m L, Andersson I, Bjurstam N, Frisell J, Rutqvist LE. Update on effects of screening mammography: authors' reply . Lancet 2002;360: 339-40.
G?tzsche PC. Screening for breast cancer with mammography: author's reply. Lancet 2001;358: 2167-8.
Miller AB. The costs and benefits of breast cancer screening. Am J Prev Med 1993;9: 175-80.
Andersson I, Aspegren K, Janzon L, Landberg T, Lindholm K, Linell F, et al. Mammographic screening and mortality from breast cancer: the Malmo mammographic screening trial. BMJ 1988;297: 943-8.
G?tzsche PC. On the benefits and harms of screening for breast cancer. Int J Epidemiol (in press).
Ries LAG, Eisner MP, Kosary CL, Hankey BF, Miller BA, Clegg L, et al, eds. SEER cancer statistics review, 1973-1999. Bethesda, MD: National Cancer Institute, 2002. (http://seer.cancer.gov/csr/1973_1999/).
Douek M, Baum M. Mass breast screening: is there a hidden cost? Br J Surg 2003;90(suppl 1):June (Abstract Breast 14).
McNoe B, Miller D, Elwood M. Women's experience of the Otago-Southland breast screening programme—a compilation of five studies. Dunedin: Hugh Adam Cancer Epidemiology Unit, 1996.
Elwood M, McNoe B, Smith T, Bandaranayake M, Doyle TC. Once is enough—why some women do not continue to participate in a breast cancer screening programme. N Z Med J 1998;111: 180-3.
Bekelman JE, Li Y, Gross CP. Scope and impact of financial conflicts of interest in biomedical research: a systematic review. JAMA 2003;289; 454-65.
Lexchin J, Bero LA, Djulbegovic B, Clark O. Pharmaceutical industry sponsorship and research outcome and quality: systematic review. BMJ 2003;326: 1167-70.
G?tzsche PC. Office of NHS cancer screening programme misrepresents Nordic work in breast screening row. BMJ 2001;323: 1131.
Schwartz LM, Woloshin S, Sox HC, Fischhoff B, Welch HG. US women's attitudes to false positive mammography results and detection of ductal carcinoma in situ: cross sectional survey. BMJ 2000;320: 1635-40.
Mateau TM. A measure of informed choice. Health Expect 2001;4: 99-108.
NHS. Breast screening, the facts. London: Health Promotion England, 2001. www.cancerscreening.nhs.uk/breastscreen/publications/ia-02.html (accessed 8 Jan 2004).
Horton R. Screening mammography: setting the record straight. Lancet 2002;359: 441-2.
Nystr?m L, Larsson LG, Wall S, Rutqvist LE, Andersson I, Bjurstam N, et al. An overview of the Swedish randomised mammography trials: total mortality pattern and the representivity of the study cohorts. J Med Screen 1996;3: 85-7.
Thornton H. Consequences of breast screening. Lancet 2000;356: 1033.
US Preventive Services Task Force. Screening for breast cancer: recommendations and rationale. Ann Intern Med 2002;137: 344-6.(Karsten Juhl J?rgensen, p)