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Harms of Screening


By reviewing Medicare claims following mammographic screening in 23,172 women older than 65 years, one study [4] found that 85 per 1,000 had follow-up testing and 23 per 1,000 had biopsies. The cancer detection rate was 7 per 1,000, so the PPV for an abnormal mammogram was 8%. For women older than 70 years, the PPV was 14%. An audit of mammograms done in 1998 at a single institution revealed that 14.7% of examinations resulted in a recommendation for additional testing (Breast Imaging Reporting and Data System category 0), 1.8% resulted in a recommendation for biopsy (categories 4 and 5), and 5.7% resulted in a recommendation for short-term interval mammography (category 3). Cancer was diagnosed in 1 out of 30 of the cases referred for additional testing.[5]

False Sense of Security

The sensitivity of mammography (refer to the Mammography section of this summary for more information) ranges from 70% to 90%, depending on a woman's age and the density of her breasts, which is affected by her genetic predisposition, hormone status, and diet. Assuming an average sensitivity of 80%, mammograms will miss approximately 20% of the breast cancers that are present at the time of screening (false-negatives). If a woman does not seek medical attention for a breast symptom or if her physician is reluctant to evaluate that symptom because she has a "normal" mammogram, she may suffer adverse consequences. Whereas the medical community has been carefully educated that a negative diagnostic mammogram should not deter work-up of a palpable lump, the medical and lay communities should be made aware that a negative screening mammogram misses one in five cancers.

Radiation Exposure

Because radiation exposure is a known risk factor for the development of breast cancer, it is ironic that ionizing radiation is our best screening tool. The major predictors of risk are young age at the time of radiation exposure and the radiation dose. For women older than 40 years, the benefits of annual mammograms may outweigh any potential risk of radiation exposure due to mammography.[6] It is speculated that certain subpopulations of women may have an inherited susceptibility to ionizing radiation damage,[7,8] but mammography has never been shown to be harmful in these, or any, subgroups. In the United States, the mean glandular dose for screening mammography is 1 mGy to 2 mGy (100-200 mrad) per view or 2 mGy to 4 mGy (200-400 mrad) per standard two-view exam.[9,10]


Because large numbers of women have false-positive tests, the issue of psychological distress-which may be provoked by the additional testing-has been studied. A telephone survey of 308 women performed 3 months after screening mammography revealed that about one-fourth of the 68 women with a "suspicious" result were still experiencing worry that affected their mood or functioning, even though subsequent testing had ruled out a cancer diagnosis.[11] Several studies,[12,13,14] however, show that the anxiety following evaluation of a false-positive test leads to increased participation in future screening examinations.[15]


WebMD Public Information from the National Cancer Institute

Last Updated: October 07, 2011
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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