Increased density of breast tissue is associated with an increased risk of breast cancer and false-positive mammography. Previous studies had not looked at potential differences in breast cancer risk by breast-tissue density after false-positive mammograms, the authors continued.
In an effort to expand on information obtained from previous studies, Henderson and colleagues queried the Breast Cancer Surveillance Consortium to identify women who underwent mammograms from 1994 to 2009. Using data from seven participating registries, investigators evaluated breast cancer risk after false-positive mammograms, taking into account different recommendations (workup with additional imaging or involving breast biopsy) and breast density.
“We hypothesized that there would be a greater increase in breast cancer risk among women with a history of false-positive biopsy recommendation results compared with those with a false-positive additional imaging recommendation and that this association would be independent of breast density,” the authors wrote.
Data analysis included 1,297,906 women ages 40 to 74 with no family history of breast cancer who underwent a total of 2,207,942 screening mammograms. The results showed 159,448 false-positive mammograms and a radiologist recommendation for additional imaging, 22,892 false-positive mammograms and a recommendation for biopsy, and 2,025602 true-negative mammograms.
Women 40 to 49 accounted for the largest proportion of false-positive mammograms with additional imaging (34.8%) or biopsy recommendation (33.1%). False-positive mammograms with additional imaging or biopsy also occurred more often among pre- and perimenopausal women and compared with the group who had true-positive results (38% to 39% versus 30%).
False-positive mammographic findings were numerically more common in women with heterogeneously or extremely dense breasts but not significantly higher as compared with women who had true-negative results (54% to 55% versus 45%).
Among women with true-negative mammographic results, 43,105 breast cancers occurred during 11,034,496 person-years of follow-up, translating into a rate of 3.91/1,000 person-years. That compared with a rate of 5.51/1,000 for women who had false-positive mammograms and a recommendation for additional imagine and 7.01/1,000 in the subgroup who had false-positive results and a biopsy recommendation. Stratification by breast density showed a similar rate pattern, lowest in the true-negative group and highest in the false-positive with biopsy group.
During the first year of follow-up, about 20% of women with false-positive and true-negative mammograms had subsequent screening mammograms. Rates were similar at 3, 4, and 5 years, suggesting that women with false-positive results were not screened more often as compared with women who had true-negative results, the authors noted.
An adjusted analysis showed that women with a false-positive mammogram and additional imaging had a hazard ratio for breast cancer of 1.39 versus women with true-negative results. False-positive mammography with biopsy was associated with a hazard ratio of 1.76 compared with women who had true-negative mammograms. Analyses by breast density yielded similar hazard ratios for women with heterogeneously or extremely dense breasts.
Even in the absence of a clear explanation for the finding, the study makes a strong case that “we should accept that a false-positive mammogram is a risk factor for predicting future risk of breast cancer,” Wender told MedPage Today.
“In clinical terms, that means women who have a false-positive mammogram need to be particularly vigilant about keeping up with regular mammographic screening. The clinicians caring for these women should have a way to track women who have had a false-positive and make sure that every effort is made to keep up to date with mammography.”
Henderson and co-authors disclosed no relevant relationships with industry.
Cancer Epidemiology, Biomarkers & Prevention