Update April 2 : I just spoke with Michael L. LeFevre, chairman of the influential U.S. Preventive Services Task Force, about the JAMA study. As I noted below, that panel is preparing to update its 2009 guidelines on breast cancer screening, probably within the next 12-18 months.

For now, its policy is that the benefits of mammograms outweigh their harms, especially for women aged 50 to 75. For women aged 40-49, it's a closer call, but the task force still tips in favor of mammography, LeFevre said.

When I asked LeFevre how he sorts out all the new information on mammograms for his patients, he put it this way: "For a woman in her 40s, I say 'let's discuss'" whether to be screened. For women aged 50-75, "I say 'I would like to recommend...But we have to acknowledge that the benefits are not as great'" as once believed. LeFevre said he tells patients aged 50 to 75 to be screened every other year.

LeFevre noted the erroneous belief that breast cancer is a disease of young women; it is more common as women get older. Women in their 40s who get annual mammograms have a 50 percent chance of a false positive at some point, he said.

If a biopsy is needlessly conducted, he said, "that's a harm. We've raised anxiety, we've created fear, we've [put the patient through] a painful procedure, all to prove she didn't have as disease."


Mammography's benefits are substantial but its potential harms may be greater than previously realized, a state of affairs that should encourage physicians and patients to make decisions about the test based on women's individual risks and preferences, researchers concluded in a new 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 -- in many cases 40 -- 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 40-49 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 are saved and among women 60 to 69, 42 lives are saved, because breast cancer--the second-leading cause of cancer deaths among females--is more common 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 result is about 61 percent for a 40- or 50-year-old woman who has annual mammograms for 10 years. Overdiagnosis is an even greater concern. The research shows a 19 percent risk that a cancer detected on a mammogram never would have caused any health problems. That could result in needless treatment such as surgery, chemotherapy or radiation for cancers that might never have been detected or threatened a woman's health.

The analysis, which appeared Tuesday in the Journal of the American Medical Association (JAMA), is the latest to cast doubt on the value of mammograms, which now 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.

In July a panel of the National Cancer Institute argued that the time had come to alter how cancer is detected, treated and defined because improved screening has resulted in the overdiagnosis and overtreatment of cancers that are not life-threatening. Breast cancer was one of the examples cited in the commentary, which also appeared in JAMA.

The influential U.S. Preventive Services Task Force is preparing to update its recommendations on breast cancer screening, issued in 2009.

"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.

Keating, who teaches at Harvard Medical School and is a primary-care physician at Brigham and Women's, said doctors can help by sitting down with patients and walking through their risk factors for cancer. The patient can then make an informed decision about being screened, and "does need to accept this very tiny risk if she decides not have mammography."