A review of 50-plus years of literature on the benefits and risks of mammography has found that while screening mammograms may reduce breast cancer mortality, the benefits of mammography are less--and the potential harms greater--than had once been expected.
Consequently, according to the article, published April 2, in the Journal of the American Medical Association, physicians and patients need more guidance on how best to individualize an approach to breast cancer screening, particularly since the benefits and harms of screening are related to a wide variety of clinical factors and personal preferences.
"What I tell my patients is that the mammogram is not a perfect test," Nancy Keating, co-author of the report and an associate professor of medicine at Brigham and Women's Hospital in Boston, said in an article published by Harvard Medical School. "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."
Keating and co-author Lydia Pace, a research fellow in women's health at Brigham and Women's, estimated that for every 10,000 women in their 40s who undergo screening for breast cancer for 10 years, 190 will be diagnosed with breast cancer. Of those 190, the authors concluded, five will avoid dying because of screening, while 25 will die regardless of whether they are screened or not.
That mortality reduction benefit needs to be weighed against the risks of overdiagnosis, Keating and Pace argued. Based on the literature review, they determined that about 19 percent of women diagnosed with breast cancer based on findings from a mammogram are overdiagnosed and receive unnecessary treatment in the form of surgery, chemotherapy and radiotherapy.
In addition, they reported that more than half the women who undergo annual screenings for more than 10 years can expect to receive a false positive mammogram that requires more imaging and the possibility of unnecessary biopsies.
"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," Pace said. "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."
In response to the article, the American College of Radiology and the Society of Breast Imaging issued a statement saying that while they agreed that breast cancer diagnosis and treatment will one day be more individualized and that patients should discuss mammography with their doctors, an approach to breast cancer screening "based primarily on risk--as discussed in the JAMA article--would miss the overwhelming majority of breast cancers present in women and result in thousands of unnecessary deaths each year."