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Breast Cancer Screening

National Institutes of Health
Consensus Development Conference Statement
September 14-16, 1977

Please see more recent conference statement 
Breast Cancer Screening for Women Ages 40-49
published in 1997

This statement is more than five years old and is provided solely for historical purposes. Due to the cumulative nature of medical research, new knowledge has inevitably accumulated in this subject area in the time since the statement was initially prepared. Thus some of the material is likely to be out of date, and at worst simply wrong. For reliable, current information on this and other health topics, we recommend consulting the National Institutes of Health's MedlinePlus http://www.nlm.nih.gov/medlineplus/.

This statement was originally published as: Breast Cancer Screening. NIH Consens Statement 1977 Sep 14-16;1(1):5-8.

For making bibliographic reference to the statement in the electronic form displayed here, it is recommended that the following format be used: Breast Cancer Screening. NIH Consens Statement Online 1977 Sep 14-16 [cited year month day];1(1):5-8.

Issues and Recommendations

In 1973-74, Breast Cancer Detection Demonstration Projects (BCDDP's) were initiated at 29 locations around the country under the auspices of the National Cancer Institute (NCI) and the American Cancer Society. Their purpose was to demonstrate the feasibility of periodic screening of large numbers of women for breast cancer, with the use of clinical history, physical examination, mammography, and thermography. Following inception of this program, however, questions were raised about the relative values of the screening components when compared to possible risks involved with the ionizing radiation from mammography. Critics suggested that the radiation used to detect cancers might also induce malignant disease at a later date. No concern was expressed or intended regarding the obvious value and importance of diagnostic X-ray examination of the breast in women with signs and/or symptoms that might be related to breast cancer.

In October 1975, NCI appointed three experts to lead investigations into various aspects of these issues, by analysis of data generated by a study conducted by the Health Insurance Plan (HIP) of Greater New York, which began in 1963. A group headed by Dr. Lester Breslow of the University of California at Los Angeles, Los Angeles, California, was to examine the benefits as determined by the HIP study results. A group chaired by Dr. Arthur Upton, then Dean of Basic Sciences, Health Sciences Center, State University of New York, Stony Brook, New York, was to consider and estimate radiation risks. Another group headed by Dr. Louis Thomas of the National Institutes of Health (NIH), Bethesda, Maryland, was to examine the pathology of cancers found in the HIP study. Subsequently, in January 1977, a working group under the leadership of Dr. Oliver Beahrs of the Mayo Clinic, Rochester, Minnesota, was charged with reviewing in depth the findings generated by the BCDDP's.

Recently, NIH and NCI convened a meeting, the NIH/NCI Consensus Development Meeting on Breast Cancer Screening, with the objective of developing a set of recommendations on the major issues and questions that have arisen concerning breast cancer screening and the BCDDP's, including mammography.

The panel (see Appendix) appointed to deliberate on these issues met in open forum at NIH on September 14-16, 1977, reviewed the reports of the four study groups mentioned above, and heard testimony from interested professionals, associations, BCDDP directors, and members of the public. The questions and a summary of the recommendations formulated by the panel follow.*

Question 1

Is there evidence that early detection of breast cancer leads to reduced mortality from breast cancer? Which of the available screening modalities or combination of modalities is most effective in early detection?

Answer

The only sound scientific evidence that demonstrates a favorable benefit in breast cancer screening is derived from the HIP study. The data from this randomized controlled trial, which formed the rationale and stimulus for the BCDDP's, indicate that periodic breast cancer screening can decrease the number of deaths due to breast cancer by about 40% in women who are over 50 years of age. The age suggests that this disease may be related to menopause, but the data in the HIP study do not permit any definition of this question. However, the HIP study thus far shows no decrease in breast cancer mortality attributable to the screening of women below 50 years of age.

The evidence indicates that the benefit of the screening program rests on the combined use of physical examination and mammography. The panel noted that no rigorous scientific data have shown to what extent either physical examination alone or mammography alone may be beneficial. The efficacy of physical examination as a screening procedure for breast cancer (e.g., by well-trained nurse practitioners) has not been examined.

The panel acknowledged that mammographic techniques have improved markedly in recent years, with smaller, and presumably earlier, lesions now being detected. The advantage of mammography lies in the fact that appropriate therapy may be administered at an earlier stage of breast cancer, which presumably improves prognosis. Moreover, radiation dosage has been decreased significantly. Nonetheless, data are insufficient to indicate that these advances have resulted in decreased mortality for women under 50 years of age at the time of screening.

Question 2

Whatare the risks of each of the available screening modalities for early detection of breast cancer?

Answer

Neither physical examination nor techniques such as thermography or ultrasound are known to have harmful effects upon the body. The use of mammography, however, is associated with an inherent risk of radiation exposure and studies indicate that breast tissue is partly susceptible to radiation damage.

The precise radiation risk is difficult to quantify, but current evidence strongly suggests that risk increases linearly with increasing dose and is linear down to the lowest dose.

At the present time, the average surface radiation exposure in the BCDDP centers is 1.2 (0.2-2.5) roentgens. It is estimated that every rad of exposure raises a woman's risk of breast cancer by about 1%. Thus, if a woman in the general population has about a 7% chance of developing breast cancer in her lifetime, one rad will increase her risk by 1% of 7%, or from 7 to 7.07%. The panel observed that even with the cumulative dose that would result from a series of five yearly mammograms in the BCDDP (approximatelty 4 rads total with the newer techniques), the increased risk of breast cancer is so little that it could not be demonstrated in long-term follow-up studies of the BCDDP group.

With repeated examinations of one cohort of women, the likelihood of finding new cancers progressively declines after prevalent cancers are detected, while the total radiation given each woman progressively rises. This puts an obvious limit on the advisability of repeated rescreening of the same population.

Question 3

Do the potential risks versus benefits differ for different methods of breast cancer detection and at different ages of patients screened?

Answer

The question of risk, in this context, applies only to mammography. Data from several studies indicate that the risk of radiation, in general, may decrease with age, although data from the analysis of A-bomb survivors show an excess of cancer in the group over 50 years old. Data suggest that the peak age of susceptibility is between 10 and 19 years and that the danger drops gradually thereafter. This possibility, too, argues for the confinement of radiation, in this instance mammography, to older age groups, but the evidence is not conclusive.

Question 4

If it is not possible to answer any or all of the foregoing questions, what data need to be generated to provide adequate answers?

Answer

New diagnostic and screening techniques are needed. The panel recommended greater emphasis on research with noninvasive techniques, such as thermography, ultrasound, and biologic markers.

Because the potential benefits of thermography remain undocumented, the panel recommended that thermography be discontinued as a routine part of the BCDDP screening program except in those centers where sufficient expertise is available to justify further clinical investigation and research. Because thermography in the BCDDP's was not set up as a research study, its continued use should require the development of a research design.

The panel deplored the lack of clear-cut data on the efficacy and the risk-benefit ratio of screening for women under 50 years of age, but they did not come to an agreement about the feasibility and logistics of randomized clinical trials to resolve such issues. However, clinical trials would be important in order to resolve certain questions concerning the efficacy of periodic breast screening.

The BCDDP's should continue to monitor all women in whom breast cancer has been diagnosed. Although the panel was unable to assess the feasibility of following all women who have had a mammogram in the BCDDP's, the members seemed to be in general agreement that such follow-up would be important and that this question deserves further consideration.

Question 5

What are the practical and ethical considerations for implementation of demonstration projects in cancer detection and how do the BCDDP's comply with these considerations?

Answer

Demonstration programs by definition utilize proven and practical methods to project new information to the medical community. However, from their inception, the BCDDP's have of necessity incorporated certain practices of assumed but unconfirmed value.

As demonstration programs with investigational components, therefore, the BCDDP's must come to grips with several important ethical concerns. The panel recommended that the Informed Consent Form used in the BCDDP's indicate the radiation dosage to be delivered to the patient and assure that all information gained through the program will be disclosed to the screenee as well as to her physician.

The panel proposed that the screenee receive the Informed Consent Form and appropriate background materials beforehand, so that she could discuss the proposed procedure with her family and her physician.

The panel recommended that the histology of any lesion smaller than l cm in diameter or any papillary or intraductal proliferation originally interpreted as malignant be reviewed by at least two pathologists prior to definitive therapy.

Women who have been screened already and who have had a diagnosis of cancer should be notified promptly if the diagnosis has been changed.

Any new experimental study should take into consideration a variety of issues, e.g., its justification from a cost-benefit point of view, the informed consent process, the way in which research subjects are selected, and the development of guidelines for compensation of individual participants who are injured in the course of the study. Furthermore, more women, both professional and consumer representatives, should be included in the design and planning of any future studies.

Question 6

What can the Consensus Development Panel recommend as to the type and frequency of breast cancer screening and as to who should provide the screening?

Answer

On the basis of the available evidence, with the understanding that no new participants are being added to the program and that limits be set on radiation exposure, the panel recommended that BCDDP Screening with combined mammography and physical examination be continued for those women who are 50 years of age and older and currently enrolled in the BCDDP's. Regardless of the location for mammographic screening, upper limits should be set on radiation exposure consistent with best current data. Women subjected to mammography should ask for such information and should be urged to maintain their own personal exposure records.

The panel found no convincing justification for routine mammographic screening for women under 50 years of age. This does not imply, however, that physical examination and breast self-examination are not important for women of any age.

The panel recommended that routine mammography for women who are 40-49 years of age and enrolled in the BCDDP's be restricted to women with a personal history of breast cancer or with a mother or sister(s) who has a history of breast cancer.

Mammographic screening of women below 40 years of age should be limited to those women having a personal history of breast cancer.

Ethical considerations, however, led the panel to concede that women who are under 50 years of age and already participating in the BCDDP's should be afforded the opportunity to continue having mammograms if they wish--so long as they are informed that no benefit has been proved, there is presumed risk, and the panel does not recommend mammographic screening in this age group. (Again, the panel went to great length to distinguish between mammographic screening and mammography used as a diagnostic tool. Thus, for example, if a woman who is under 50 years of age and enrolled in the BCDDP develops symptoms or observes changes suggestive of breast cancer, she may well require mammographic examinations as part of her medical evaluation by her own physician.)  


Footnote

*Throughout its deliberations, the panel repeatedly emphasized the distinction between mammography used for diagnosis--the value of which was not in question--and mammographic screening to detect possible disease in women who have no symptoms or clinical signs whatsoever.


 

Conference Panel

Samuel Thier, M.D., Chairman
Professor and Chairman Department of Internal Medicine Yale University
New Haven, Connecticut
Virgil Loeb. M.D., Vice-Chairman
Associate Professor, Clinical Medicine
Washington University School of Medicine
St. Louis, Missouri
Kenneth Casebeer, J.D.
Assistant Professor of Constitutional Law
Miami University law School
Coral Gables, Florida
Archie Cochrane
Professor
Medical Research Council Epidemiology Unit
Cardiff, Wales, Great Britain
Willie Dell
Richmond Councilwoman
Richmond, Virginia
Milton Elkin, M.D.
Professor and Chairman of Radiology
Albert Einstein College of Medicine
New York, New York
Sister Margaret Farley
Yale School of Religious Studies
Divinity School
New Haven, Connecticut
Emil Frei III, M.D.
Director and Physician-in-Chief
Sidney Farber Cancer Institute
Boston, Massachusetts
Patricia R. Hall
6205 Lombard Street
Cheverly, Maryland
Raffaele Lattes, M.D.
Professor of Surgical Pathology
College of Physicians & Surgeons
Columbia University
New York, New York
Brian MacMahon, M.D.
Professor of Epidemiology
Harvard School of Public Health
Boston, Massachusetts
George Mishtowt, M.D.
5454 Wisconsin Avenue Suite 925
Chevy Chase, Maryland
Francis D. Moore, M.D.
Elliott Carr Cutler Professor of Surgery
Harvard Medical School
Department of Surgery
Boston, Massachusetts
Edward Radford, M.D.
Professor of Environmental Epidemiology
University of Pittsburgh
Pittsburgh, Pennsylvania
Leo Rigler, M.D.
Professor of Radiological Sciences
University of California
Center for Health Sciences
Los Angeles, California
Jane Wright, M.D.
Professor of Surgery
New York Medical College
New York, New York

Conference Sponsors

National Cancer Institute

American Cancer Society

Office of Medical Applications of Research

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