Mammograms: Should I or shouldn t I? And how often?

There has lately been much debate about how often women should be screened for breast cancer. In 2009 the U.S. Preventive Services Task Force (USPSTF) recommended that the standard age for routine screening be raised from 40 to 50, while advising that the frequency be reduced from yearly to once every other year. Still, adherence to the recommendation is at the discretion of doctors and patients, which means that many are still trying to decide the most reliable course to follow. Accordingly, a recent study published in the Annals of Internal Medicine looked more closely at the implications of the recommendations. The researchers found that, in considering an annual mammogram, women and their doctors must balance the unnecessary anxiety and potential harm that could come from an increased likelihood of false-positives with the benefits that result from increased vigilance.

Researchers from the Group Health Center for Health Studies in Seattle looked at data from the Breast Cancer Surveillance Consortium, the most comprehensive breast cancer registry in the world, comparing the cumulative probability of false-positive results and stage of cancer diagnosis after 10 years of either annual or biennial screening. They concluded that, after a decade of annual screening, more than half of women screened will have at least one false-positive. Biennial screening resulted in only a 35 percent incidence of false positives, but that was accompanied by a small increase in the probability of late-stage cancer diagnosis. They also found that, while digital mammography was slightly more likely to detect cancer in women ages 40 to 49, this method also increased the risk of false positive results, compared to regular film-screen mammography.

One of the co-authors observed that her research team conducted these studies to help women understand that having a false positive result is part of the process for mammography screening. ACSH's Dr. Ross agrees that the study is valuable in that respect. Women and their families might eventually experience less stress and anxiety if they understand the frequency with which false-positives appear, he says.

Dr. Ross also believes that the study underscores what plain statistics do not: Mammograms do reduce the rate of breast cancer mortality, but those simple statistics don t measure the havoc wreaked on bodies and nerves by false positives, which become more common as the frequency of screening increases, and which can lead to repeat screenings, invasive biopsies, and even unnecessary mastectomies. If this study clarifies those risks for doctors and patients, it s done a good thing.