It happens to millions of women — they come in for a mammogram, the radiologist sees something suspicious, orders a follow-up x-ray or ultrasound, and it turns out to be nothing.
It's distressing, takes up a lot of time and can cost money. But a new study suggests it may be worth paying attention to these visits. Women who had false-positives were more likely to actually develop breast cancer down the road.
Women who got a false positive were 39 percent more likely to get breast cancer over the next 10 years than women who simply got a negative result on a mammogram, Louise Henderson of the University of North Carolina-Chapel Hill and colleagues found.
Women whose x-rays looked serious enough to get them sent for a biopsy were 76 percent more likely to later have an actual breast cancer diagnosis, they reported in the journal Cancer Epidemiology, Biomarkers & Prevention.
"We also found that women with a history of a false-positive result continued to have an increased risk of developing breast cancer 10 years after experiencing the false-positive result," Henderson said in a statement.
Having a suspicious-looking mammogram that's serious enough to merit a biopsy is already a known risk for future breast cancer, notes Dr. Therese Bevers of the MD Anderson Cancer Center in Houston. "(These are) not entirely surprising findings as we have long known that women with benign breast disease on biopsy are at increased risk of developing breast cancer," she said.
The National Cancer Institute's breast cancer risk calculator includes it as a risk factor. It also includes a woman's age, race, whether she has had radiation treatment to the chest, when and whether she's had children, when she reached puberty and whether she has close relatives with breast cancer.
Henderson said maybe having a false positive on a mammogram should also now enter the equation.
"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," her team wrote.
Henderson's team looked at 2.2 million screening mammograms done for 1.3 million women over 40.
It might be that the mammogram is spotting pre-cancerous changes in the breast tissue, she said. "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," she said.
"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."
A woman's absolute risk of breast cancer is still fairly low. The women who should take the most care are those with so-called dense breasts. "The highest risk of breast cancer observed in our study was among women with extremely dense breasts who had false-positive results with a biopsy recommendation," Henderson's team wrote.
Breast cancer is a leading killer of U.S. women. Every year, it's diagnosed in 200,000 women and a few men, and kills around 40,000. But it's only diagnosed in one in eight women in the U.S. over their lifetimes.
Mammograms are an annual chore for millions of American women, considered so important that federal law mandates that most health insurance plans pay for them without charging the patient anything.
But there is still a debate about when and how often women should get them.
Just this year the American Cancer Society revised its mammogram guidelines, saying most women can start at age 45. The U.S. Preventive Services Task Force says most women can safely wait until they are 50 to start getting mammograms and that they need only one every other year.
At least one study has showed that many women suffer intense anguish after they get called for a follow-up mammogram when a radiologist has spotted something suspicious.
Henderson doesn't want to add to that worry.
"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."