Breast cancer screening.

Randomized controlled trials involving nearly 500,000 women on two continents have confirmed the early promise that screening mammography can reduce breast cancer mortality. The observed benefits of mammographic screening, however, are not the same in all women. The mortality reduction in women over age 70 is unknown, and women aged 40 to 49 do not appear to benefit from mammographic screening to the same extent as those over age 50. The reasons for this disparity are incompletely understood, but it depends in part upon differing tumor biology and mammographic test characteristics in younger women. Even if relative survival benefits were equal for women under and over age 50, absolute reduction in risk would remain considerably lower for younger women, a disparity that would not be corrected by improved screening technology or adjustment of interscreening intervals. The authors' review of the evidence leads them to strongly support mammographic screening of women aged 50 to 69 at an interval not longer than 2 years. The authors also feel it is reasonable to screen women over age 70 who have a favorable life expectancy. They conclude, however, that the evidence does not support a blanket recommendation in favor of screening women aged 40 to 49. Instead, they advocate a well-informed conversation between physician and patient regarding the present knowledge and the risks and benefits of screening for each individual woman. Definitive answers await the results of ongoing RCTs designed to study the survival benefit conferred by screening women aged 40 to 49. Disagreement will undoubtedly persist regarding which recommendations should determine private practice and public policy.