Women with a history of a false-positive mammogram result may be at increased risk of developing breast cancer for up to 10 years after the false-positive result, according to a study led by a researcher at the University of North Carolina at Chapel Hill.
“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, Dr. Louise M. Henderson, adjunct professor of epidemiology at the UNC Gillings School of Global Public Health, assistant professor of radiology at the UNC School of Medicine, and member of the UNC Lineberger Comprehensive Cancer Center. “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.”
[Photo: Women with a history of a false-positive mammogram may be at increased risk of developing breast cancer for up to 10 years after the false-positive result, a UNC researcher found. However, the study findings should not cause women to feel anxious about mammograms and breast health, as the increase in absolute risk related to a false-positive mammogram is modest. The finding is intended to be one useful tool in the context of other risk factors assessing overall breast cancer risk.]
The study was published December 2 in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
In the United States, 67 percent of women ages 40 and older undergo screening by mammography every one to two years, Dr. Henderson said. Prior studies have shown that about 16 percent of first mammograms and 10 percent of subsequent mammograms will generate a false-positive result.
During the course of 10 screening mammograms, the chance of at least one false-positive result is 61 percent for women screened annually, and 42 percent for women screened every two years, Dr. Henderson explained.
For this study, Dr. Henderson and colleagues analyzed data from the Breast Cancer Surveillance Consortium (BCSC) from 1994 to 2009. The study population, which came from seven registries in different parts of the U.S., included 2.2 million screening mammograms performed in 1.3 million women from 40 to 74 years old. The Carolina Mammography Registry, which draws on data from imaging facilities across the state and housed at UNC, was one of the seven registries included in the study.
After the initial screening, women in the study were tracked across 10 years. During this period, 48,735 of the women were diagnosed with breast cancer.
After a mammogram, women showing some evidence of suspicious tissue typically will be referred for additional imaging, and some of those women will be further referred for a breast biopsy, said Dr. Henderson.
After adjusting for common factors that influence breast cancer risk, Henderson and colleagues found in their study that women whose mammograms were classified as false-positive who were referred for additional imaging had a 39 percent increased chance of developing subsequent breast cancer during the 10-year follow-up period, compared with women with a true-negative result. Women whose mammograms were classified as false-positive but were referred for a breast biopsy had a 76 percent increased chance of developing subsequent breast cancer compared with women with a true-negative result.
Dr. Henderson also examined whether breast density affected the relationship between false-positive mammograms and subsequent breast cancer, using the BI-RADS breast density categories of almost entirely fat, scattered fibroglandular densities, heterogeneously dense and extremely dense.
“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. This was not surprising, as increased breast density is known to make mammograms more difficult to read.
Breast density did not affect the relationship between false-positive mammograms and subsequent cancer for most women.
Recent research has shown that women who experience false-positive mammograms tend to feel anxious and may develop negative effects on behavior and sleep. Dr. Henderson said she does not want the study findings to increase anxiety over mammograms and breast health because the increase in absolute risk with a false positive mammogram result is modest.