High Rate of False-Positives with Annual Mammogram

By Elizabeth Fernandez, Public Affairs | October 17, 2011

During a decade of receiving mammograms, more than half of cancer-free women will be among those summoned back for more testing because of false-positive results, and about one in 12 will be referred for a biopsy.

K.KerlikowskeSimply shifting screening to every other year lowers a woman’s probability of having one of these false-positive episodes by about a third – from 61 percent to 42 percent – over the course of a decade.

Karla Kerlikowske, MD

A new study delving into false-positives in mammography looked at nearly 170,000 women between the ages of 40 and 59 from seven regions around the United States, and almost 4,500 women with invasive breast cancer. Because of the added decade of testing alone, it found, women who start mammograms at 40 instead of 50 are more likely to have false-positive results that lead to more testing.

“This study provides accurate estimates of the risk of a false-positive mammography and breast biopsy for women undergoing repeat mammography in community practice, and so provides important information about the potential harms of undergoing regular mammography,” said co-author Karla Kerlikowske, a professor of medicine at the UCSF School of Medicine.

The study will be published in Annals of Internal Medicine. The research was led by Group Health Research Institute of Seattle for the Breast Cancer Surveillance Consortium.

“Recalls’’ for a second mammogram for what turn out to be non-cancer results, known as false positives, may cause inconvenience and anxiety. Recommendations for fine-needle aspiration or surgical biopsy are less common, but can lead to unnecessary pain and scarring. The additional testing also contributes to rising medical costs.

Kerlikowske is the lead author of an additional report – to be published in the same issue of Annals – that for the first time in the United States examines the accuracy of film mammography against digital, which has increasingly replaced older film screening.

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