Mammogram study shows higher risks

Mammography's benefits are substantial, but its potential harms may be greater than previously realized, which should prompt physicians and patients to make decisions about the screening test based on women's individual risks and preferences, researchers concluded in a recent study.

Lydia Pace and Nancy Keating, both associated with Boston's Brigham and Women's Hospital, said women should move away from guidelines that call for them to begin having mammograms at a particular age - 40, in many cases - and be screened at frequent intervals. Instead, they should weigh the benefits and risks of mammography with their physicians and determine their tolerance for the uncertainty that may accompany skipping the exam.

"The take-home for the average woman is, first of all, that there is no right answer about mammography screening," said Pace, a research fellow in global women's health at Brigham and Women's. "The data that we have are not perfect, and they are mixed. But they do strongly suggest that although mammography does have benefits, it does also have a lot of harms, and those harms are not insubstantial."

In a search of studies that went back to 1960, the researchers determined that for every 10,000 women aged 40 to 49 who receive regular mammograms, five lives would be saved by the discovery of cancers that otherwise would go undetected. For women aged 50 to 59, 10 lives would be saved, and among women 60 to 69, 42 lives would be saved. The risk of breast cancer, the second-leading cause of cancer deaths among females, increases as women age. Overall, the screenings are associated with a 19 percent reduction in mortality, the researchers wrote.

But at the same time, the cumulative risk of a mammogram resulting in a false positive is about 61 percent for a 40- or 50-year-old woman who has annual mammograms for 10 years. That could result in needless surgery, chemotherapy or radiation.

The analysis, which appeared in the Journal of the American Medical Association, is the latest to cast doubt on the value of mammograms, which account for $8 billion in annual health care expenditures in the United States, according to an editorial in the same edition. A study of 90,000 women released in February found that death rates from breast cancer and other causes were the same for women who had mammograms as for those who didn't.

"As a society … we really, really want to have a way to detect breast cancer early and decrease breast cancer mortality," Pace said. It is "profoundly disappointing that mammography doesn't quite live up to its promise," she added.

"We both also feel it does not show as strong a benefit as is often suggested in the media and has been suggested by previous screening" regimens.