Earlier, more frequent mammograms equal more false-positive results
March 20, 2013 | by Hiu Chung So
Start at 40 or start at 50? Once a year or every other year? These are the questions women — and their doctors — are asking about mammograms as screening guidelines and recommendations are continually revised and debated.
The latest round of studies is far from the final word, but it highlights an issue associated with earlier, more frequent screenings: False-positive mammograms lead to unnecessary worries and invasive biopsies.
The first study, published online in JAMA Internal Medicine on March 18, analyzed data from more than 900,000 women who underwent screening mammograms from 1994 through 2008. The data were sorted for screening frequency, breast density, age and hormone therapy use and evaluated for late-stage breast cancer diagnoses and false-positive cancer diagnoses.
Even after accounting for breast density and hormone therapy use, researchers found that for women ages 50 to 74, having a mammogram every other year did not lead to a higher likelihood of detecting an advanced-stage breast cancer compared to women who received an annual mammogram. In fact, only women ages 40 to 49 with extremely dense breasts showed a benefit of having annual examinations.
Meanwhile, for multiple groups, an annual screening mammogram did increase the likelihood of a false-positive result. This led the study’s authors to write: "Women aged 50 to 74 years, regardless of breast density or [hormone therapy] use, can undergo biennial rather than annual mammography.” Even women 40 to 49 with extremely dense breasts should weigh the likelihood of catching breast cancer earlier against the risk of higher false-positive chances, they concluded.
Looking at the study’s results, Laura Kruper, M.D., director of City of Hope's Rita Cooper Finkel and J. William Finkel Women’s Health Center, told TIME.com that “the study did surprise me ... I am one of the ones saying every woman must have [a] mammogram every year at 40.”
Kruper, who was not involved in the study, did appreciate that the paper used advanced breast cancer diagnosis — rather than mortality — as the end point. "Our therapies are so good for breast cancer, that even if it is detected later on, a patient can still do well,” she said.
In a separate study in the Annals of Family Medicine, a survey of more than 450 women showed that a false-positive diagnosis is more than just a minor mishap from which a woman quickly recovers. The survey consisted of multiple psychosocial measures, including impacts on sleep and sexuality, general anxiety, worries about a future breast cancer diagnosis and the questioning of existential values.
After conducting and analyzing the three-year survey, researchers found that even after being declared “cancer free” for years, women who had received a false-positive result reported greater psychosocial harm compared to those who had had a normal, negative mammogram.
Matthew Loscalzo, M.S.W., Liliane Elkins Professor in Supportive Care Programs, provided outside commentary on the findings to HealthDay, noting that the study concurred with his personal experience working with women who had a false-positive diagnosis worrying “will the next [test result] be a breast cancer?”
Sally Shaw, M.D., radiologist and chief of City of Hope's Breast Imaging Section, also provided external comments about these findings. While acknowledging that women should be educated about mammograms’ limitations and potential for false-positives, she continues to advocate earlier and more frequent screenings.
“It is known that mammography can find early cancers. It isn’t perfect, but it’s the best we have,” she told the Los Angeles Times.
Currently, the American Cancer Society advises that women 40 and older should undergo an annual mammogram for early breast cancer detection.