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 or not to have regular breast cancer screenings beginning at age 40. That troubling finding is based on the latest review of research conducted by Harvard Medical School and Brigham and Women’s Hospital researchers, which concluded 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 to a 32 percent reduction for older 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 Brigham and Women’s Hospital. She and her colleague Dr. Nancy Keating, an associate professor of health care policy at Harvard Medical School, found that the lifesaving benefits of mammograms are smaller than researchers previously thought and the harms -- like repeat screenings and biopsies for findings that turn out not to be cancer -- are greater.
They calculated that 10 in 10,000 women in their 50s who are screened every year for a decade will avoid a breast cancer death; 6130 women, on the other hand, will have a false positive result that requires extra X-rays and 940 will have biopsies for non-malignant findings.
About one in five women whose cancers are detected via mammograms -- before any lump or swelling can be felt -- will be over-treated for breast cancers that never would have been found otherwise and never would have become life-threatening.
“For many physicians, conveying nuance and uncertainty may be difficult, especially when patients accept or expect clear answers,” wrote Dr. Joann Elmore of Harborview Medical Center in Seattle, and Dr. Barnett Kramer of the National Cancer Institute, in an editorial that accompanied 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 substantial chance of having additional mammograms or an unnecessary biopsy is dwarfed in comparison to the far smaller possibility of having their life saved by the screening.
Women grappling with whether or not to have an annual screening can consider their own individual risk, Pace said, since certain factors like family history, advanced age, and delaying child-bearing until later in life -- or avoiding it altogether -- can increase breast cancer risk. Women with dense breast tissue, which can be detected on a baseline mammogram, or those who have had previous lumps biopsied are also at increased risk.
Mammography rates for women in their 40s haven’t budged much since a government-sponsored task force of prevention experts advised in 2009 that doctors stop recommending the screening to women under age 50. That’s likely because doctors keep endorsing them as a sure-fire way to catch breast cancer at its earliest most curable stage.
Both the American College of Obstetricians and Gynecologists -- whose members often write mammogram referrals -- and the American Cancer Society continue to recommend that women age 40 and older have annual mammograms. Updated recommendations from the cancer society are expected later this year, Wender said.
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.