Breast cancer is the most common cancer, other than skin cancer, among women in the United States. It's also the second-leading cause of cancer death, behind lung cancer. In the past several years, various task force recommendations and studies have questioned the benefits of broad screening guidelines for mammograms, disagreeing over how often to screen, when women should start screening and when they should stop.
The waters become especially muddy when experts discuss the potential harm caused by “overdiagnosing” cancer – that is, the number of false-positive results or abnormalities that are treated unnecessarily.
A new review of 50 years worth of studies published recently in the Journal of the American Medical Association is unlikely to clear up those waters: The study concluded that the benefits of mammograms are often overstated and the harms minimized. But the study also confirmed, again, what many experts, including those at City of Hope – have been saying: Screening decisions must be tailored to the specific risks and medical histories of each woman.
“Risk assessment is really very critical,” Joanne Mortimer, M.D., director of the Women’s Cancers Program at City of Hope, has said. “We harp on individualized health care, and that means understanding each woman’s risk. At low risk, don’t expose them to radiation unnecessarily. Women at very high risk, by all means, they may need mammograms and they may also need an MRI.”
The new review, co-authored by Harvard Medical School and Brigham and Women’s Hospital, analyzed mammogram data from 1960 to 2014, assessing data from eight large randomized controlled trials. The researchers found that mammography was associated with a 19 percent overall reduction in the risk of dying from breast cancer, with about a 15 percent reduction for women in their 40s and about 32 percent for women in their 60s.
The benefits of mammograms depend on personal breast cancer risk, and all women share the risk of overdiagnosis, according to the study. For example, if a group of women between the age of 40 and 50 received yearly mammograms for a decade, more than 60 percent could expect a false-positive. In addition, about 19 percent of the cancers detected through mammograms would not have been apparent or harmful without screening.
Women should speak with their doctors about the individual risk and determine the screening plan that is best for them.
High-risk patients typically receive breast cancer screening every six months, alternating between MRI scans and mammograms. About 5 to 10 percent of breast cancer cases are considered hereditary, and women who carry one of the known gene mutations may be at an 80 percent higher risk of developing breast cancer and may warrant more aggressive screening than women at low risk. Other women who may be at elevated risk include those who have been exposed to chest radiation, who have had a prior cancer or who have a strong family history of breast cancer.
Learn more about the Women's Cancers Program at City of Hope.