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Avoidable Exposures: Patients

Fighting for a safer environment at home, in the community, and at work

Dangers and Unreliability of Mammography: Breast Examination is a Safe, Effective, and Practical Alternative

Samuel S. Epstein, Rosalie Bertell, and Barbara Seaman

International Journal of Health Services, 31(3):605-615, 2001.

Mammography screening is a profit-driven technology posing risks compounded by unreliability. In striking contrast, annual clinical breast examination (CBE) by a trained health professional, together with monthly breast self-examination (BSE), is safe, at least as effective, and low in cost. International programs for training nurses how to perform CBE and teach BSE are critical and overdue.

Contrary to popular belief and assurances by the U. S. media and the cancer establishment- the National Cancer Institute (NCI) and American Cancer Society (ACS)- mammography is not a technique for early diagnosis. In fact, a breast cancer has usually been present for about eight years before it can finally be detected. Furthermore, screening should be recognized as damage control, rather than misleadingly as "secondary prevention."

Mammography poses a wide range of risks of which women worldwide still remain uninformed.

Radiation Risks
Radiation from routine mammography poses significant cumulative risks of initiating and promoting breast cancer (1- 3). Contrary to conventional assurances that radiation exposure from mammography is trivial- and similar to that from a chest X-ray or spending one week in Denver, about 1/ 1,000 of a rad (radiation-absorbed dose)- the routine practice of taking four films for each breast results in some 1,000-fold greater exposure, 1 rad, focused on each breast rather than the entire chest (2). Thus, premenopausal women undergoing annual screening over a ten-year period are exposed to a total of about 10 rads for each breast. As emphasized some three decades ago, the premenopausal breast is highly sensitive to radiation, each rad of exposure increasing breast cancer risk by 1 percent, resulting in a cumulative 10 percent increased risk over ten years of premenopausal screening, usually from ages 40 to 50 (4); risks are even greater for "baseline" screening at younger ages, for which there is no evidence of any future relevance. Furthermore, breast cancer risks from mammography are up to fourfold higher for the 1 to 2 percent of women who are silent carriers of the A-T (ataxia-telangiectasia) gene and thus highly sensitive to the carcinogenic effects of radiation (5); by some estimates this accounts for up to 20 percent of all breast cancers annually in the United States (6).

Cancer Risks from Breast Compression
As early as 1928, physicians were warned to handle "cancerous breasts with care- for fear of accidentally disseminating cells" and spreading cancer (7). Nevertheless, mammography entails tight and often painful compression of the breast, particularly in premenopausal women. This may lead to distant and lethal spread of malignant cells by rupturing small blood vessels in or around small, as yet undetected breast cancers (8).

Delays in Diagnostic Mammography
As increasing numbers of premenopausal women are responding to the ACS's aggressively promoted screening, imaging centers are becoming flooded and overwhelmed. Resultingly, patients referred for diagnostic mammography are now experiencing potentially dangerous delays, up to several months, before they can be examined (9).

Falsely Negative Mammograms
Missed cancers are particularly common in premenopausal women owing to the dense and highly glandular structure of their breasts and increased proliferation late in their menstrual cycle (10, 11). Missed cancers are also common in post-menopausal women on estrogen replacement therapy, as about 20 percent develop breast densities that make their mammograms as difficult to read as those of premenopausal women (12).

Interval Cancers
About one-third of all cancers- and more still of premenopausal cancers, which are aggressive, even to the extent of doubling in size in one month, and more likely to metastasize- are diagnosed in the interval between successive annual mammograms (2, 13). Premenopausal women, particularly, can thus be lulled into a false sense of security by a supposedly negative result on an annual mammogram and fail to seek medical advice.

Falsely Positive Mammogram
Mistakenly diagnosed cancers are particularly common in premenopausal women, and also in postmenopausal women on estrogen replacement therapy, resulting in needless anxiety, more mammograms, and unnecessary biopsies (14, 15). For women with multiple high-risk factors, including a strong family history, prolonged use of the contraceptive pill, early menarche, and nulliparity- just those groups that are most strongly urged to have annual mammograms- the cumulative risk of false positives increases to "as high as 100 percent" over a decade's screening (16).

Overdiagnosis and subsequent overtreatment are among the major risks of mammography. The widespread and virtually unchallenged acceptance of screening has resulted in a dramatic increase in the diagnosis of ductal carcinoma-in-situ (DCIS), a pre-invasive cancer, with a current estimated incidence of about 40,000 annually. DCIS is usually recognized as micro-calcifications and generally treated by lumpectomy plus radiation or even mastectomy and chemotherapy (17). However, some 80 percent of all DCIS never become invasive even if left untreated (18). Furthermore, the breast cancer mortality from DCIS is the same- about 1 percent- both for women diagnosed and treated early and for those diagnosed later following the development of invasive cancer (17). That early detection of DCIS does not reduce mortality is further confirmed by the 13-year follow-up results of the Canadian National Breast Cancer Screening Study (19). Nevertheless, as recently stressed, "the public is much less informed about over-diagnosis than false positive results. In a recent nationwide survey of women, 99 percent of respondents were aware of the possibility of false positive results from mammography, but only 6 percent were aware of either DCIS by name or the fact that mammography could detect a form of 'cancer' that often doesn't progress" (20).

Quality Control
In 1992 Congress passed the National Mammography Standards Quality Assurance Act requiring the Food and Drug Administration (FDA) to ensure that screening centers review their results and performance: collect data on biopsy outcomes and match them with the original radiologist's interpretation of the films (21). However, the centers do not release these data because the Act does not require them to do so. It is essential that this information now be made fully public so that concerns about the reliability of mammography can be further evaluated. Activist breast cancer groups would most likely strongly support, if not help to initiate, such overdue action by the FDA.

Despite the long-standing claims, the evidence that routine mammography screening allows early detection and treatment of breast cancer, thereby reducing mortality, is at best highly questionable. In fact, "the overwhelming majority of breast cancers are unaffected by early detection, either because they are aggressive or slow growing" (21). There is supportive evidence that the