False-Positive Results for Screening Mammograms and Clinical Breast Examinations Reported in The New England Journal of Medicine

American Cancer Society
Wednesday, 15 April 1998

A new study published by researchers at the University of Washington and Harvard Medical School in the April 16, 1998 issue of The New England Journal of Medicine examines the risk of false positive results from mammography and clinical breast examinations. The study found that over a 10-year period, one out of three women who had screening mammograms and clinical breast exams had at least one false-positive mammogram. A false-positive mammogram means that additional testing after an abnormal result determined that these women did not have cancer (specifically, that no cancer was diagnosed within one year after the abnormal exam). The study was supported in part by the American Cancer Society.

According to the researchers, one out of two women will receive at least one false-positive result after having annual mammograms for a decade, and almost 20 percent of women will undergo a biopsy (either fine needle aspiration, open, or core biopsies). The study also suggests that almost 25 percent of women will have a false-positive result at some point in 10 years of clinical breast exams. The researchers note that women who receive abnormal results have to undergo additional tests that may be time-consuming and costly, and also that studies show some women who have abnormal screening results experience increased anxiety and stress about breast cancer.

Robert Smith, PhD, of the Cancer Control Department at the American Cancer Society, comments, "We need to reduce the rate of abnormal interpretations, and especially the frequency of avoidable biopsies. Because breast cancer is among women's leading health concerns, greater effort should be made to safely minimize the rate of abnormal exams, and when a woman does receive an abnormal interpretation, we need to be more mindful that this is stressful news. Finally, women should know what to expect from screening, that although mammography is highly accurate, it is not perfect. Some women will have abnormalities that are eventually determined not to be breast cancer, and a small percentage of women with breast cancer will not have their cancer seen on a mammogram. However, at this time, our emphasis should be on improving the quality of mammography, and fully informing women about the benefits and limitations of this test."

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