Many mammograms turn out to be false positives.
Women are usually elated when they find out that the test was wrong. But a new study shows that these false positives are linked to later tumors.
Reuters reports on mammogram false alarms.
A mammogram is deemed a false positive when it shows possible breast cancer but supplemental screenings or a biopsy fails to find it. New research shows that women whose screening mammograms produce false alarms have a heightened risk of being diagnosed with breast cancer years later, but the reason remains an enigma.
A higher danger of breast cancer among women with a ‘false positive’ mammogram has been issued before. What is new about this study is that the researchers involved tried to figure out how much, if any, of the additional risk is actually due to doctors missing the cancer the first time they tested the troubling mammogram results.
My von Euler-Chelpin, an epidemiologist who led the study, told Reuters,
“Mistakes from doctors missing cancers explained only a small percentage of the increased risk.”
How was the study conducted? Out of over 58,000 Danish women who had mammography between 1991 and 2005, her study found 4,743 women with curious results that were eventually found to be negative.
What were the results?
In 2008 researchers found that 295 of those 4,743 women had been diagnosed with breast cancer, and this finding was reported in Cancer Epidemiology.
“Radiologists reread the original mammograms and found that doctors had actually missed the cancer in 72 of the 295 women, for a false-negative rate of 1.5 percent. Even after taking those missed cancers into account, however, the researchers found that women with false-positive mammograms were still 27 percent more likely to be diagnosed with breast cancer years later, compared to women with only negative test results. The risk was higher in women who had surgical biopsies that turned out to be negative,” according to Reuters.
The study’s author, Von Euler-Chelpin, finds that a percentage of American women would have a higher risk for breast cancer after a false-positive test because the U.S. has a higher rate of false positives than Denmark. The danger of a false positive test over ten mammograms conducted ranges from fifty-eight percent to seventy-seven percent in the United States; whereas that number is around sixteen percent in Denmark according to the research.
Reuters asked other experts, who were not involved in the study, what they thought of the study such as Dr. Alvarado, a breast cancer surgeon from the University of California in San Francisco.
He said he agreed that the danger of being diagnosed with breast cancer after a false positive mammogram is most likely lower in the United States than in Denmark.
He also found that,
“It’s hard to translate the data to the U.S. population because we have such a different screening program, we tend to biopsy everything, and we’re much more aggressive. Is there some inherent biology of the breast that makes it suspicious and it puts you at higher risk? I don’t think anyone knows what it.” Alvarado also speculated if women who get false-positive mammograms should be more regularly examined and scrutinized by their physicians, or if false-positive patients should be screened in some other manner.
Another expert, Dr. Kerlikowske agreed with the study author’s point about the need to personalize breast cancer screening programs for women. She was not involved in the study. Dr. Kerlikowske is producing a risk calculator app to help lead women in deciding how often to get mammograms. The calculator takes into account a broad number of factors, including age, race, previous breast cancer, family history and breast density.
Reuters reports, “The average five-year breast cancer risk for a 50-year-old white woman with no prior family history of breast cancer is 1.25 percent, the calculator shows.
It ranges from less than 1 percent, to 2.70 percent, depending upon breast density, for the same woman with a history of a prior breast biopsy, regardless of whether the biopsy was positive or negative.”
Federal health agencies still recommend that women over forty regularly get screened for breast cancer even if the overall risk of testing positive is low. It is still difficult for physicians to determine who is at a higher risk of developing breast cancer (unless they have the BRCA gene), as everyone’s medical history is different.
The American Cancer Society suggests that women be screened for breast cancer every year they are in good health starting at the age of forty. “But a growing number of researchers have questioned the benefits of annual mammograms, and since 2009 the government-backed United States Preventive Services Task Force has recommended that screening be done every two years and be generally restricted to women aged 50 to 74. The recommendation to reduce the frequency and delay the start of mammography screening was based on research showing the risk of false-positive results – which needlessly expose women to the anguish of a possible breast cancer diagnosis and the ordeal of further testing – outweighed the benefits of detecting cancers earlier,” according to Reuters.