Breast cancer: mammogram
The test: a mammogram, which is a specialized x-ray of the breast.
The guidelines: The task force calls for women between ages 50 and 74 to get a mammogram every two years, saying there's not enough evidence to support a recommendation for or against the test later in life. But the American Cancer Society advises annual mammograms beginning at age 40 and continuing as long as a woman is in good health.
What to consider: The prevention task force, in making its recommendations, looked at clinical-trial data showing a 15 percent reduction in breast cancer deaths as a result of mammography screening among women in their 40s, 50s and 60s. It weighed this benefit against potential harms, including the stress of a false positive leading to further testing, but also the possibility of "overdiagnosis"—the identification and, presumably, treatment of cancers that would not have become a problem during the woman's lifetime. Estimates of overdiagnosis vary widely. One recent analysis by Danish researchers claimed that as many as a third of breast cancers identified through screening programs would not have caused harm; the task force analysis reported rates of between 1 and 10 percent.
For women in their 40s, when breast cancer is less common and false positives more likely due to dense breasts, the task force concluded the drawbacks of mammography outweighed the benefits—a highly controversial 2009 decision.
For women age 75 and older, the issue is partly a simple lack of data to support a benefit from screening, says Mara Schonberg, M.D., of Beth Israel Deaconess Medical Center in Boston, whose research focuses on decisions about mammography among older women. In addition, as life expectancy wanes, harms may outweigh the benefits of early detection and treatment of cancers that may be slow-growing.
Next: Colonoscopy. »