Breast Cancer Screening Guidelines Robert A. S m i t h , P h D Senior Director, Detection Programs Professional Education Department American Cancer Society, National Office Atlanta, Georgia

he establishment, periodic review, and modification of guidelines for breast cancer screening reflect an intent to communicate to women and health care providers basic information related to appropriate ages and periodicity for breast examinations. Although there is an absence of consensus among all medical groups over when screening should begin, when it should end, and the appropriate intervals for screening for women in different age groups, there is little dispute over the combined value of regular mammography and clinical examination for the early detection of breast cancer.

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BREAST CANCER SCREENING GUIDELINES In a recent overview of the history of breast cancer screening guidelines, Dr. Gerald Dodd ~ pointed out that prior to 1977 there were no specific guidelines to indicate at what ages and intervals women should undergo screening tests for breast cancer. Several years earlier, the initial publications of early results from the Health Insurance Plan of New York (HIP) study provided support for the use of mammography in the early detection of breast cancer, and in 1973 the American Cancer Society and the National Cancer Institute launched the Breast Cancer Detection Demonstration Project (BCDDP) to demonstrate that breast cancer screening could be implemented on a large scale. 2~ By 1975 there were 29 participating sites in 27 geographic areas, with more than 280,000 women between the ages of 35 and 74 enrolled in the project. However, concerns about the absence of a clear benefit from mammography in w om en under age 50 and the potential risks from exposure to radiation, especially for younger women, led to the convening of a consensus development meeting at the National Cancer Institute in 1977. The deliberations at that meeting led to the decision to limit the use of mammography in the BCDDP to w om en age 50 and over, unless women under age 50 had a personal history of breast cancer or a first-degree relative with breast cancer. 7,8 Women under age 40 would be candidates for mammography only if they had a personal history of breast cancer. These first guidelines for breast cancer screening were endorsed by the American Cancer Society, and the Society also added criteria 212

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for physical examinations of the breast, including breast self-examination and clinical breast examination.t In the 15 years since these first consensus guidelines for screening were established, the American Cancer Society has modified its guidelines on four occasions, based on careful consideration of new data related to the sensitivity of mammography and average radiation dose during the examination. By 1980, continued analysis from HIP and new data available from the BCDDP suggested that a revision in the guidelines for breast cancer screening were in order. In guidelines issued for the cancer-related checkup,* it was recommended that: 1. Women older than age 20 should perform monthly breast self-examination. 2. Women from 20-40 years of age should have a physical breast examination every 3 years, and women older than 40 years should have a physical breast examination every year. 3. Women from 35-40 years of age should have a baseline mammogram, although women younger than 50 years should consult their physicians about the need for mammography in their individual cases. 4. Women older than 50 years of age should have a mammogram every year. 9 These guidelines also recommended that women with a personal or family history of breast cancer should consult their physicians about the value of more frequent examinations or about the need to begin mammography before 50 years of age. Three years later, in 1983, two findings from the BCDDP were judged sufficient to warrant reconsideration of the guidelines. First, a significant proportion of all cancers detected were among women age 35-49 (including many in situ cancers), and there was agreement that the quality of mammography had also significantly improved. At this point in the study, survival experience was regarded as sufficiently favorable to indicate the likelihood that screening offered benefits to women under age 50. Therefore, the American Cancer Society modified the guidelines for asymptomatic women between the ages of 40 and 49 to include mammography at intervals of between 1-2 years. Earlier recommendations about the relevance of family history in establishing a screening interval remained in effect. During the 1980s, the growing interest in mammography led a number of organizations to issue guidelines to their membership; some of these guidelines were different than those issued by the American Cancer Society and the American College of Radiology. For this reason, between 1987 and 1988, the American College of Radiology convened several meetings, bringing representatives from these organizations together to work toward a set of consensus guidelines for breast cancer screening. Although some organizations declined in the end to be represented among the consensus group, a press conference was held in 1989 to announce the agreement among 12 organizations that breast cancer screening should begin by age 40 and consist of annual clinical breast examination and mammography at 1-2-year intervals. After age 50, women should be screened with clinical breast examination and mammography annually. Again, this reconsideration of the recommendations, especially for women between the ages of 40 and 49, was based on continued long-term analyses from the HIP and BCDDP studies, which, in the judgment of these 12 organizations, indicated a benefit for women between the ages of 40 and 49. The baseline mammogram was not regarded as essential if regular screening began by age 40. The advocacy of breast self-examination was left to individual organizations. In the fall of 1991, the American Cancer Society convened a Workshop on Guidelines and Screening for Breast Cancer to reconsider its guidelines and address several key issues. These included: 1) the rationale for the baseline

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study between the ages of 35 and 39; 2) the recommendations for age and periodicity, specifically the rationale for screening women under age 50; 3) the evidence for increasing the frequency of screening among women under age 50 and decreasing the frequency of screening in postmenopausal women; and 4) the issue of an upper age limit for mammography.* After a day of scientific presentations, work groups met to address the issues that had been raised. At the conclusion of the meeting, it was the recommendation of the work groups that there were insufficient new data to recommend significant change in the guidelines. The exceptions were the recommendations that annual or biannual mammography begin by age 40 and that the baseline mammogram between the ages of 35 and 39 could be deleted. 1°-13For both women age 40-49 and women 50 years of age and older, the work groups concluded that recent data were insufficient at this time to warrant any changes in the guidelines, although these issues may be revisited in the future when additional data from ongoing clinical trials and new data from the National Breast Cancer Screening Study in Canada become available. However, although not significantly modifying the guidelines, the working groups addressed a number of issues related to the guidelines, and they offered additional guidance. For example, there had been concern that the absence of an upper age limit in the recommendations for screening led to ad hoc decisions that women at ages older than 75 were not candidates for screening. The work groups strongly asserted that the average woman of older age has significant projected longevity and that unless comorbidity indicates otherwise, screening for breast cancer is appropriate.

CRITERIA FOR GUIDELINES AND CONTROVERSIES There is little question that differences in the guidelines issued by different organizations and countries reflect different criteria and differences in the weighing of evidence. Not all organizations in the United States share the guidelines recommended by the American Cancer Society, the American College of Radiology, and ten other organizations, and the primary basis for disagreement t relates to the recommendation to screen women under age 50 with mammography. 1.14 For women age 50 and older, the evidence from two clinical trials clearly supports the efficacy of mammography. ~-~8 The evidence from these same studies, however, is less clear for women under age 50. To date, other than two analyses of HIP data, none of the randomized controlled trials have shown a statistically significant benefit from mammography for women between the ages of 40 and 49. Analysis of the HIP data has demonstrated approximately a 25% reduction in mortality for women under age 50 at 10 and 18 years of follow-up, but the significance of these results, both statistical and practical, remains a source of disagreement. 19,20 Our ability to quantify the benefits of mammography for women under age 50 from studies done to date is limited in other ways. For example, each of the studies applied a different screening modality, ie, combination of single- or two-view mammography, annual or biannual examinations, or with or without clinical breast examination. The frequency of mammography, number of views, and the inclusion of clinical breast examination may be more critical factors in the sensitivity of mammography in women under age 50 compared with women age 50 years and older. Because none of the studies completed to date was specifically designed to test the efficacy of mammography in women under age 50, the relatively small size of this subgroup in each study also limits our ability to draw conclusions about efficacy. There is also little question that the quality of 214

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*Proceedings from the W o r k s h o p on Guidelines a n d Screening for Breast Cancer, October 1991, P a s a d e n a , California, are available as a Professional Education Publication from the A m e r i c a n Cancer Society (92-5M-No.3041-PE). tFor example, in e v a l u a t i n g clinical preventive services, i n c l u d i n g breast cancer screening, the U.S. Preventive Services Task Force established as its m a i n criteria for the value of a preventive service that evidence for clinical effectiveness existed from at least o n e well-designed r a n d o m i z e d controlled trial. 14'1s

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mammography has vastly improved since the HIP study was initiated. Thus, the potential benefits of these improvements in image quality to women under age 50 are being judged using a historic standard of imaging that might, at the time, have been comparatively ineffective for younger women. These limitations in our ability to draw unqualified conclusions from the clinical trial and other studies completed to date imply a situation of uncertainty with respect to screening women under the age of 50.

CONCLUSION Guidelines for breast cancer screening have been profoundly influenced by the results from randomized clinical trials, and for some organizations, trial results more heavily influence guidelines than does other scientific evidence. Guidelines from other organizations also are based on the results of trials, but additionally are informed by results from other study designs, on the basis that these data can be evaluated for the implications they bring to improving the public's health. For example, the similar and very favorable stage and survival experience among women age 40-49 and 50-59 diagnosed with breast cancer in the BCDDP (as well as additional evidence from the BCDDP and other studies) was regarded as sufficient by the 12 organizations that issued consensus guidelines to include the recommendation that women age 40-49 be screened with mammography. The randomized clinical trial is the gold standard for testing a hypothesis. However, the outcomes of randomized clinical trials, like any study design, are not immune from the influence of sample size, design, and execution. Additionally, human subjects often behave in ways that are in conflict with the scientific needs of the investigators. Women randomized to screening may choose not to participate. Women not invited to screening may elect to be screened for breast cancer anyway. Results, however, must be evaluated for the study and control arms of the trial regardless of the degree of compliance of the subjects. It has been argued that randomized clinical trials can be a mixed blessing, because for all their scientific advantages, they can become a roadblock to progress by creating a climate in which change awaits the results of another trial. This is fine if the trial is underway or if there is strong commitment to fund the trial and there is acceptance that the establishment of guidelines will await the results. Even if a trial is underway, or near the point where early results will be published, concerns about study design and protocol may mean that the results are judged as flawed and of little value to inform important guidelines issues. This may be the case with the long-awaited results of the National Breast Cancer Screening Study being conducted in Canada, as judged by the controversies and ongoing debates prior to the publication of study results. 21-28 With respect to the question regarding the benefits of mammography in women under age 50, the important question to ask and to answer in a quantifiable manner is, why wouldn't mammography offer a benefit to women in this age group and, if the benefits are negligible, what must we do to improve early detection and treatment for that age group? With respect to this age group, we should ask whether adequate randomized controlled trial data are forthcoming, and if they are not (because of lack of funding or scientific priority, or due to the presence of a medical-legal climate where the opportunity for testing new hypotheses may no longer exist), then continued analysis of existing trial data and quasi-experimental designs may offer the only opportunity to decide the issue of efficacy of screening women under the age of 50. Mammography in women under 50 may remain controversial

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for reasons other than efficacy, ie, comparative benefits, costs, etc. H o w e v e r , at this time, m a m m o g r a p h y offers the only potential to detect breast cancer prior to the onset of clinical s y m p t o m s both in w o m e n age 40-49 a n d w o m e n age 50 a n d older. The question of w h y early detection in y o u n g e r w o m e n w o u l d not be as effective as early detection in older w o m e n , or u n d e r w h a t clinical circumstances those same benefits could be achieved, remains to be more clearly answered.

REFERENCES 1. Dodd GD. American Cancer Society guidelines on screening for breast cancer: An overview. CA 1992;42:177-80. 2. Shapiro S, Strax P, Venet L. Periodic breast cancer screening in reducing mortality from breast cancer. JAMA 1971;215:1777-85. 3. Strax P, Venet L, Shapiro S. Value of mammography in reduction of mortality from breast cancer in mass screening. Am J Roentgenol Radium Ther Nucl Med 1973;67:686-9. 4. Shapiro S, Venet W, Strax P, Venet L. Periodic screening for breast cancer: The Health Insurance Plan Project and its sequelae, 1963-1986. Baltimore: Johns Hopkins Press, 1988. 5. Baker LH. Breast cancer detection demonstration project: Five-year summary report. CA 1982;32:194-225. 6. Seidman H, Gelb SK, Silverberg E, LaVerda N, Lubera JA. Survival experience in the breast cancer detection demonstration project. CA 1987;37:258-90. 7. National Cancer Institute. Consensus development meeting on breast cancer screening (National Cancer Institute Publication [NIH] 78-1257). Washington, DC: US Department of Health, Education, and Welfare, Public Health Service, 1977 Sept. 8. National Cancer Institute/American Cancer Society. Report of the working group to review the National Cancer Institute-American Cancer Society breast cancer detection demonstration projects. J Nat Cancer Inst 1979;62:640-709. 9. Guidelines for the cancer-related checkup: Recommendations and rationale. CA 1980;30:194-240. 10. Mettlin CJ, Heath CW, Chu KC, et al. Biologic variations, incidence by age, and risk assessment of breast cancer screening outcomes. CA 1992;69 Suppl:19992000. 11. Shapiro S, Smart CR, Costanza ME, et al. Guidelines for breast cancer screening. CA 1992;69 Suppl:2001-2. 12. McKenna RJ, Greene P, Winchester DP, et al. Breast self-examination and breast physical examination. CA 1992;69 Suppl:2003-4. 13. Smith RA, Black BL, Price GW, et al. Legal aspects, legislative effect, cost effectiveness, and barriers to breast cancer screening. CA 1992;69 Suppl:2005-7. 14. Woolf SH. United States Preventive Services Task Force recommendations on breast cancer screening. CA 1992;69 Suppl:1913-8. 15. US Preventive Services Task Force. The report of the US Preventive Services Task Force. Baltimore: William and Wilkins, 1989. 16. Shapiro S. Evidence on screening for breast cancer from a randomized trial. Cancer 1977;39 Suppl:2772-82. 17. Tabar L, Fagerberg CJG, Gad A, et al. Reduction in mortality from breast cancer after mass screening with mammography: Randomized trial from the Breast Cancer Screening Working Group of the Swedish National Board of Health and Welfare. Lancet 1985;1:829-32. 18. Tabar L, Fagerberg G, Duffy SW, Day NE. The Swedish two county trial of mammographic screening for breast cancer: Recent results and calculations of benefit. Epidemiol Community Health 1989;43:107-14. 19. Chu KE, Smart CR, Tarone RE. Analysis of breast cancer mortality and stage distribution by age for the Health Insurance Plan clinical trial. J Natl Cancer Inst 1988;80:1125-32. 20. Day NE, Baines CJ, Chamberlain J, et al. UICC project on screening for cancer:

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21. 22. 23. 24. 25. 26. 27. 28.

Report of the workshop on screening for breast cancer. Int J Cancer 1986;38:3038. Breast cancer screening in women under 50 [editorial]. Lancet 1991;337:1575-6. Miller AB. Breast cancer screening in women under 50 [letter]. Lancet 1991;338:1134. Baines CJ, Miller AB, Kopans DB. Canadian national breast screening study: Assessment of technical quality by external review. AJR Am J Roentgenol 1990;155:7437. Merz B. Author of Canadian breast study retracts warnings. J Natl Cancer Inst 1992;84:832-4. Miller AB. Re: "Author of Canadian breast cancer study retracts warnings." J Natl Cancer Inst 1992;84:1365-6. Warren L. Response. J Natl Cancer Inst 1992;84:1366-7. Kopans DB. Response. J Natl Cancer Inst 1992;84:1367-8. Moskowitz M. Response. J Natl Cancer Inst 1992;84:1368-71.

A S S E S S M E N T OF C U R R E N T S C R E E N I N G G U I D E L I N E S

The development of breast cancer screening guidelines and, in particular, the recommended intervals between screening mammography have, as Robert A. Smith, PhD, outlined, been an evolving process (paper printed above). Consensus guidelines were drawn up in 1989 in response to concerns within the medical community about the necessity of speaking with one voice. Those guidelines, the ones we live with today, were forged jointly by the American College of Radiology, the American Cancer Society, and the National Cancer Institute. One year ago, the American Cancer Society held one of its periodic reviews of the consensus guidelines. Representatives were present from many major organizations. They concluded that the recommendation calling for mammograms every 1-2 years for women age 40-49 was based upon minimal data, but that there was insufficient evidence to warrant any changes in the guidelines at that time. Continued monitoring of all available evidence was recommended. One source of additional evidence is the as yet unpublished but widely leaked data from the Canadian National Breast Screening Study (NBSS). The methodology and some of the conclusions of that study were reviewed by Dr. Baines (paper printed above). Its findings suggest there is no benefit in terms of reduced mortality when women age 40-49 undergo mammographic screening; in fact, there was a greater incidence of mortality among the screened groups than among the controls. The bulk of discussion was given over to a critique of the NBSS (insofar as details are available) and a comparison of mammographic quality and patient populations in the United States and Canada. Gerald M. Dodd, MD, served as moderator. Is it possible that the excess deaths among women age 40-49 years in the screened group are the result of unintentional randomizing errors that resulted in a disproportionate number of advanced cancers being included in the screened arm of the trial?

Dr. Baines was asked to respond to several points raised by Daniel Kopans, MD, concerning the NBSS. She acknowledged the above possibility, but noted that the NBSS findings in this regard duplicate those of other studies, most notably the Swedish two-county study conducted by Tabar et al. "I find it very strange that it's an observation that can be made in more than one study, and I think it's essential that we start trying to understand why that paradoxical finding did occur," she said. She did acknowledge that the excess

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Breast cancer screening guidelines.

Breast Cancer Screening Guidelines Robert A. S m i t h , P h D Senior Director, Detection Programs Professional Education Department American Cancer S...
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