Half of all women who get mammograms regularly will have a “false positive” within 10 years—a “suspicious” finding that turns out to not be cancer after all. When they find out that their “positives” are false, they’re relieved.
But a large new study shows that women who get false positives may be at higher risk for breast cancer after all. Researchers analyzed data from 1.3 million women aged 40 to 74. Compared with women who had only negative mammograms, those who had had false positives were 39% more likely to get breast cancer in the next 10 years—and those who had gotten biopsies because of their potentially positive results were 76% more likely to get breast cancer.
Researchers aren’t sure why false positives would be an indicator of greater cancer risk, but it’s possible that what medical science currently labels as “false” results could actually indicate changes in breast tissue that are not cancer but that stand a reasonable chance of developing into it.
The increased risk percentages sound scary but the actual level of risk for women who had false positives is much smaller than you might think. That’s because the vast majority of women, even those who have had false-positive mammogram results, don’t get breast cancer. In the study, women with true negative mammograms had a 10-year risk of developing breast cancer of 0.4%, while those with a false positive had a 0.5% risk, and those who had a false positive and then a biopsy had a 0.7% risk. Even in the highest-risk biopsy group, then, 99.3% will not get breast cancer in the next decade.
It may be that as the science improves, some of today’s mammogram results that are simply considered “false positives” and forgotten about will come to be considered actual positives—not for cancer, but for increased risk, albeit small.
Women with a strong family history of breast cancer, especially those with genetic markers for the disease, are already at higher-than-average risk. While this study didn’t look at these groups of women in particular, they already have reason to be extra vigilant.
For women who aren’t aware of any extra risk, however, this study may be an added incentive—if you’ve ever had a false-positive mammogram result, you now have even more reason to monitor your breast health.
To learn about that—and much more—see Bottom Line’s Breast Cancer Guide: Prevent, Detect, Treat, Recover.