Medical groups issue differing mammogram schedules for women in their 40s and older

Deciding when to start routine mammograms and how often to repeat them remains unsettled, with major medical groups offering different recommendations for women in their 40s and beyond. The latest guidance, issued by the American College of Physicians last month, advises average-risk women ages 50 to 74 to get mammograms every other year, while telling women ages 40 to 49 to discuss the pros and cons with a doctor before choosing whether to be screened, and if they do, to screen every other year.

The disagreement reflects a challenge inherent to screening: breast cancer guidelines are built around women who are considered “average risk” and have no symptoms. Yet breast cancer is common, and risk can vary widely, making it difficult to define who is truly average and how to balance potential benefits against harms. “Breast cancer is not one disease,” said Dr. Laura Esserman of the University of California, San Francisco, adding that a one-size-fits-all approach may not match differing risk levels.

In the United States, more than 320,000 women are expected to be diagnosed with breast cancer this year, according to the American Cancer Society. Death rates have fallen for decades,...