While screening mammograms aren’t perfect, they are the best way we have right now to detect breast cancer early, when it’s most treatable.
When a screening mammogram shows an abnormal area that looks like a cancer but turns out to be normal, it’s called a false positive. Ultimately the news is good: no breast cancer. But the suspicious area usually requires follow-up with more than one doctor, extra tests, and extra procedures, including a possible biopsy.
A large study suggests that women with false-positive mammogram results have a slightly higher risk of developing invasive breast cancer within the next 10 years.
The research was published online on Dec. 2, 2015 by the journal Cancer Epidemiology, Biomarkers & Prevention. Read the abstract of “Increased Risk of Developing Breast Cancer after a False-Positive Screening Mammogram.”
To do the study, the researchers looked at information from nearly 1.3 million women ages 40 to 70 with no family history of breast cancer who had screening mammograms from 1994 to 2009. The information came from the Breast Cancer Surveillance Consortium database, which is maintained by the National Cancer Institute.
The researchers found that the 1,297,906 women had a total of 2,207,942 screening mammograms. There were:
- 159,448 false-positive results with a recommendation for more imaging
- 22,892 false-positive results with a recommendation for biopsy
- 2,025,602 negative mammograms
Women ages 40 to 49 made up the largest percentage of false-positive mammogram results with a recommendation for more imaging (33.1%). Women with dense breasts also were more likely to have false-positive results.
The researchers then compared the rates of invasive breast cancer between women who had false-positive mammogram results and women who had negative mammogram results:
- there were 3.91 invasive breast cancers per 1,000 person-years of follow-up among women with negative mammogram results
- there were 5.51 invasive breast cancers per 1,000 person-years of follow-up among women with false-positive mammogram results with a recommendation for more imaging
- there were 7.01 invasive breast cancers per 1,000 person-years of follow-up among women with false-positive mammogram results with a recommendation for biopsy
The researchers said the 10-year risk of invasive breast cancer was:
- 39% higher in women with false-positive results with a recommendation for more imaging
- 76% higher in women with false-positive results with a recommendation for biopsy
compared to women with negative results.
It’s important to know that the increases above are increases in relative risk -- the risk of a woman with a false-positive result relative to the risk of a woman with a negative result.
In terms of absolute risk, the increase is small:
- women with false-positive results have about a 2% risk of developing invasive disease in the 10 years after the false-positive result
- women with negative results have about a 1% risk of developing invasive disease in the 10 years after the negative result
The researchers didn’t offer an explanation about why false-positive mammogram results appear to be linked to a slightly higher risk of invasive disease. Many experts think that the subtle changes suggested on the mammogram may be an early clue to cancer before actual cancer exists.
It’s also important to know that this association has been suggested in other studies. But the large number of women in the study and the length of follow-up add more evidence that the link between false-positive results and a somewhat higher risk of invasive disease actually exists.
"The power of this study to show the association is very strong, particularly when you combine it with the results of the other studies that have been done," said Richard Wender, M.D., chief of cancer control at the American Cancer Society, in an interview. "I think we can now say with confidence that women who have had a previous false-positive mammogram are at somewhat higher risk for breast cancer."
The researchers who did this study want to incorporate false-positive mammogram results into models that predict breast cancer risk.
"Now that we have this information, our hope is that we can add it into existing risk-prediction models to improve their ability to discriminate between women who will go on to develop breast cancer and those who won't," said Louise Henderson, Ph.D., of the University of North Carolina Lineberger Comprehensive Cancer Center, who was the lead author of the study. "We should accept that a false-positive mammogram is a risk factor for predicting future risk of breast cancer.
"In clinical terms, that means women who have a false-positive mammogram need to be particularly vigilant about keeping up with regular mammographic screening," she continued. "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."
It’s important to know that a false-positive mammogram result doesn’t mean you will be diagnosed with breast cancer.
"Having any history of breast biopsies is associated with a higher risk," said Breastcancer.org Chief Medical Officer Marisa Weiss, M.D. "Breast tissue that is dense or has proliferative changes tends to lead to questions on the breast imaging. Sometimes it leads to biopsies. In contrast, breast tissue that is boring, without any extra activity, rarely leads to any kind of biopsy. That kind of inactive breast tissue is less likely to develop breast cancer."
"This study doesn’t suggest that having a false-positive leads to breast cancer," said Brian Wojciechowski, M.D., Breastcancer.org’s medical adviser. "Rather, it reflects an association between breast cancer risk and abnormal breast imaging. Women should not worry that getting mammograms will increase their risk of breast cancer in the future."
There's only one of you and you deserve the best care possible. Don't let any obstacles get in the way of your regular screening mammograms, especially if you’ve had a false-positive result.
- If you're worried about cost, talk to your doctor, a local hospital social worker, or staff members at a mammogram center. Ask about free programs in your area.
- If you're having problems scheduling a mammogram, call the National Cancer Institute (800-4-CANCER) or the American College of Radiology (800-227-5463) to find certified mammogram providers near you.
- If you find mammograms painful, ask the mammography center staff members how the experience can be as easy and as comfortable as possible for you.
- If you’re concerned about unknown results or being called back for more testing, talk to your doctor about what happens when mammogram results are unclear, as well as what to expect if you’re called back for more testing.
For more information on mammograms and other tests to detect and diagnose breast cancer, visit the Breastcancer.org Screening and Testing section.