A new study could intensify the debate about the value of mammograms in screening for breast cancer, particularly for women in their 40s.
The study, researchers at Harvard Medical School’s Department of Health Care Policy and Brigham and Women’s Hospital, revealed that mammograms do save lives, but fewer than previously thought.
It also stated that the risks of regular mammography screening are larger than previously estimated.
Researchers reviewed 50 years of international studies that looked at the risks and benefits of mammography screenings. They concluded that the reduction in mortality from breast cancer was 19 percent due to annual screening for all women.
Women in their 40s, however, saw a 15 percent reduction, while women in their 60s saw a 32 percent drop in mortality, the study reported.
The researchers caution that the benefits of screening depend on an individual’s predisposition to develop the disease, while the risks of screening, namely over diagnosis, are shared among all women.
“While we need more research on mammography’s benefits and harms today, existing data suggest that we have been overestimating the benefits of mammography and underestimating the harms over the years,” said co-author Lydia Pace, research fellow in Women’s Health at Brigham and Women’s in a statement
“It is really important to have informed discussions with our patients to help them understand the chances that a mammogram will benefit them as well as the possible downsides of getting a mammogram, so that they can incorporate their own values and preferences in making the right decision for themselves,” she said.
According to a 2010 study
, most women reported discussing the benefits of cancer screening with their doctors, but few discussed the drawbacks.
Despite a controversial 2009 recommendation by the U.S. Preventive Services Task Force (USPSTF) that women begin regular screenings at 50, the rate of screening has not dropped.
Dr. Joann Elmore of Harborview Medical Center in Seattle, and Dr. Barnett Kramer of the National Cancer Institute, writing in an editorial
accompanying the Harvard study, wrote “For many physicians, conveying nuance and uncertainty may be difficult, especially when patients accept or expect clear answers.”
The Harvard study found that of 10,000 women in their 40s who have annual mammography for 10 years, roughly 190 will be diagnosed with breast cancer.
Of those, five will “avoid death from breast cancer due to screening,” the study said, and 25 of the 190 would die of breast cancer with or without screening.
The rest, the study said, would survive because of better treatment of the disease.
While those benefits are not trivial, but neither are the risks of overdiagnosis, according to the researchers. About 19 percent of women who are diagnosed via mammogram are overdiagnosis, the researchers said. That translates into roughly 36 of the 190 women could receive unnecessary surgery, chemotherapy or radiotherapy.
Still, a 19 percent reduction works out to about 7,600 lives saved. The American Cancer Society (ACS) estimates that about 40,000 U.S. women will die of breast cancer this year.
“I thought [the Harvard study] was a very good effort and approach to organizing older data into a way that clinicians and patients can use to better understand the benefits and drawbacks of mammography screening, particularly for women in their 40s,” said Richard C. Wender, M.D., chief cancer control officer with the ACS.
Wender added that his goal was to highlight areas where there is universal agreement about breast cancer screening.
“There agreement that all women over 50 should undergo screening every one to two years,” he said, adding that there is also agreement that women in their 40s should be screened or they should discuss screening with their clinicians.
“No group says don’t discuss and don’t screen,” he said. “That’s being a little misunderstood.”
The ACS recommends women age 40 and older have annual mammograms, but Wender said updated recommendations are expected later this year.
“What I tell my patients is that the mammogram is not a perfect test,” said Nancy Keating, co-author of the report, associate professor of Health Care Policy at HMS and associate professor of medicine at Brigham and Women’s in a statement
. “Some cancers will be missed, some people will die of breast cancer regardless of whether they have a mammogram, and a small number of people that might have died of breast cancer without screening will have their lives saved.”
Despite mammography’s increased scrutiny, Wender points out that of all the years of life lost due to breast cancer, 34 percent of those years occur in women who were diagnosed in their 40s.
The study was published in the Journal of the American Medical Association