Doctors may have oversold the benefits of mammography and underplayed its risks, which has left many women unable to make an informed decision about whether to have regular breast cancer screenings beginning at age 40, Boston researchers said, based on a review of recent studies.
Researchers from Harvard Medical School and Brigham and Women’s Hospital concluded that the lifesaving benefits of mammograms are smaller than researchers previously thought and the harms — including repeat screenings and biopsies for findings that turn out not to be cancer — are greater.
They found that mammograms decrease a woman’s risk of dying from breast cancer by a modest 19 percent. Women in their 40s had just a 15 percent reduction in their breast cancer death risk, compared with a 32 percent reduction for women in their 60s, who are far more likely to get breast cancer than younger women, according to the study published Tuesday in the Journal of the American Medical Association.
None of the trials could determine whether mammograms reduced a woman’s risk of dying from any cause. Certain chemotherapy drugs, for example, damage the heart muscle and raise the risk of dying from heart disease.
“There’s a lot of confusion out there, and we wanted to find a way to synthesize the literature and present it in a coherent way to doctors,” said study coauthor Dr. Lydia Pace, a research fellow in women’s health at the Brigham.
Pace and Dr. Nancy Keating, an associate professor of health care policy at Harvard Medical School, calculated that 10 in 10,000 women in their 50s who are screened every year for a decade will avoid a breast cancer death; 6,130 women, on the other hand, will have a false positive result that requires extra X-rays, and 940 will undergo biopsies for nonmalignant findings.
About 1 in 5 women whose cancers are detected via mammograms — before any lump or swelling can be felt — will be overtreated for breast cancers that never would have been found otherwise and never would have become life-threatening, the study found.
“For many physicians, conveying nuance and uncertainty may be difficult, especially when patients accept or expect clear answers,” Dr. Joann Elmore of Harborview Medical Center in Seattle and Dr. Barnett Kramer of the National Cancer Institute wrote in an editorial accompanying the study.
A 2010 study that surveyed 460 women found that more than 96 percent of them reported discussing the benefits of breast cancer screening with their physician, but fewer than 20 percent recalled discussing any negative effects of the screening.
“When I have mammography discussions with patients, I tend to emphasize the benefits over the risks,” said Dr. Richard Wender, chief cancer control officer for the American Cancer Society, who is a primary care physician. For most women, he added, the possibility of having their life saved by the screening outweighs the worry about the substantial chance of having additional mammograms or an unnecessary biopsy.
Women grappling with whether to have an annual screening can consider their own individual risk, Pace said, since certain factors such as family history, advanced age, and delaying child-bearing until later in life — or avoiding pregnancy altogether — increase breast cancer risk. Women with dense breast tissue or those who have had previous lumps biopsied, are also at increased risk.
“After looking at mammography’s pros and cons, I think many women will still want to be screened, particularly those in their 50s and 60s,” said Dr. Michael Barry, president of the Informed Medical Decisions Foundation in Boston. “Outside this age range, getting screened requires more thought.”
Mammography rates for women in their 40s have not budged much since a government-sponsored task force of prevention experts advised in 2009 that doctors stop routinely recommending the screening to women under age 50. That is probably because doctors keep endorsing the test as the best tool available to catch breast cancer at its earliest, most curable stage.
The American College of Obstetricians and Gynecologists and the American Cancer Society continue to recommend that women age 40 and older have annual mammograms.
CORRECTION: Because of a reporting error, an earlier version misstated the number of women in their 50s who would avoid a breast cancer death through annual mammogram screening. It is 10 in 10,000 women in their 50s.