A review of five decades’ worth of international studies assessing the benefits and harms of mammography screening suggests that the benefits of screening are often overestimated, while harms are underestimated. The findings, say the researchers, indicate that physicians and patients need more guidance on how best to incorporate a patient’s risk profiles and preferences into breast cancer screening decisions. The review by investigators in the Department of Health Care Policy at HMS and Brigham and Women’s Hospital appeared in the April 2 issue of JAMA.
In 2009, the U.S. Preventive Services Task Force, employing an evidence-based analysis of the benefit-risk ratio of mammography, reversed its previous recommendation that women be screened every one to two years beginning at age 40, and instead recommended routine mammography every two years from age 50 on. That change remains controversial; in fact, recent evidence suggests that mammography use in the United States has not changed to reflect the updated recommendation.
“I tell my patients that the mammogram is not a perfect test,” says Nancy Keating, an HMS associate professor of health care policy, associate professor of medicine at Brigham and Women’s, and the study’s co-author. “Some cancers will be missed, some people will die of breast cancer regardless of having had a mammogram, and a small number of people who might have died without screening will have their lives saved.”
According to Keating, the chief harm associated with mammography is the risk of overdiagnosis: identifying cancers that never would have become problematic during a woman’s lifetime, either because the cancer never grew or because the patient died first of another cause. Overdiagnosis can expose women to unnecessary surgery, chemotherapy, or radiotherapy. In addition, more than half of women who get annual screenings for a decade can expect to receive false positive reports. About 20 percent of false positives result in unnecessary biopsies.