A study released late on Monday supports controversial recommendations that women only get mammograms every other year, starting at age 50.
The report, published in Annals of Internal Medicine, found that more than half of women who get an annual mammogram would get a so-called false positive over 10 years – causing anxiety, unnecessary retesting, and perhaps painful biopsies.
Women screened every other year were not more likely to have advanced cancer than women screened every year, the researchers found – suggesting little downside to having mammograms less often.
“We conducted this study to help women know what to expect when they get regular screening mammograms over the course of many years,” Rebecca Hubbard of the Group Health Research Institute in Seattle, who helped lead the study, said in a statement.
The researchers said they looked at the medical records of 170,000 women aged 40 to 59, and another 4,500 women with breast cancer.
In 2009, the U.S. Preventive Services Task Force caused a furor when it recommended that women get mammograms every other year, starting at age 50. Most groups advise women to start at 40 and to get mammograms every year. The idea is to catch breast cancer early, when it is easy to treat.
But the downside is the false positive – when the mammogram, which is a fairly crude x-ray, seems to show a lesion, and additional imaging and perhaps even a biopsy is needed to see if a shadow on the x-ray is a tumor.
“We wanted to understand better how likely false-positive test results are when women receive annual screening mammograms compared to every other year—and starting at age 50 compared to age 40,” Hubbard said.
Over 10 years, more than half the women in the study got a false positive, and 1 in 12 got a biopsy, a painful procedure involving a needle.
When women were screened every other year, this lowered the probability of a false positive from about 61 percent over 10 years to 42 percent. “We found that women in their 40s and 50s had similar risks of having a false positive during 10 years of screening,” Hubbard said. “But over the course of a lifetime, starting screening at age 40 would make a woman more likely to have false positives than if she had started at age 50, because of that extra decade of screening.”
The women who did develop breast cancer did not appear to suffer from having waited. The breast cancer patients who had been screened only every other year were not significantly more likely to be diagnosed with late-stage cancer compared to those screened with a one-year interval, Hubbard’s team found.
Unnecessary screening not only costs money – it can cause patients anxiety. The 2010 health care law requires insurers to pay for mammograms without charging patients any fees, such as a copay. Medicare will pay for its patients to have a mammogram every year.