Breast cancer risk increases after a false-positive mammogram

By John Murphy, MDLinx
Published December 2, 2015

Key Takeaways

Women who had a false-positive screening mammogram are at increased risk of developing breast cancer for at least the following 10 years, according to a study of more than 1 million women published online December 2, 2015 in the journal Cancer Epidemiology, Biomarkers & Prevention.

This finding suggests that a false-positive screening result may be useful in predicting a woman’s breast cancer risk, the authors noted.

“Our finding that breast cancer risk remains elevated up to 10 years after the false-positive result suggests that the radiologist observed suspicious findings on mammograms that are a marker of future cancer risk,” said the study’s lead author, Louise M. Henderson, PhD, Assistant Professor of Radiology at the University of North Carolina School of Medicine in Chapel Hill, NC. “Given that the initial result is a false positive, it is possible that the abnormal pattern, while noncancerous, is a radiographic marker associated with subsequent cancer.”

Over the course of 10 screening mammograms, the chance of at least one false-positive result is 61% for women screened annually, and 42% for women screened every two years, Dr. Henderson said.

In this study, Dr. Henderson and colleagues analyzed data from the Breast Cancer Surveillance Consortium (BCSC) between 1994 and 2009. The study population included 1.3 million women ages 40 to 74 years whose screening mammogram resulted in a false-positive with recommendation for additional imaging, false-positive with recommendation for biopsy, or true-negative with no cancer.

The women were followed for more than 10 years, during which time 48,735 of them were diagnosed with breast cancer.

The researchers found that women whose mammograms were classified as false-positive and were referred for additional imaging had a 39% increased risk of developing breast cancer during the 10-year follow-up period compared with women with a true-negative result. Women whose mammograms were false-positive but were referred for biopsy had a 76% increased risk of developing subsequent breast cancer compared with women with a true-negative result.

A false-positive result is worrisome on its own, and these findings are not intended to increase anxiety over mammograms and breast health, Dr. Henderson said. She noted that the increase in absolute risk with a false-positive mammogram result was modest. 

“We don’t want women to read this and feel worried,” she said. “We intend for our findings to be a useful tool in the context of other risk factors and assessing overall breast cancer risk.”

The researchers also considered whether breast density affected the relationship between false-positive mammograms and later breast cancer. “A higher proportion of false-positive results were present among women with heterogeneously or extremely dense breasts compared with women who had almost entirely fatty breasts or scattered fibroglandular densities,” Dr. Henderson said. But this was not surprising because increased breast density can make mammograms more difficult to read, she said.

Nevertheless, breast density was not a factor for false-positive mammograms and subsequent cancer for most women, the researchers found.

“Our next steps are to consider how to incorporate a prior false-positive mammogram and biopsy results into risk-prediction models for breast cancer,” she added, noting that age, race, family history of breast cancer, history of a breast biopsy, and mammographic breast density are also significant factors in determining a woman’s risk in the BCSC risk calculator.

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