Years: Comparison of Relative and Absolute Benefit

In randomized controlled trials, screening mammography has been shown to reduce mortality from breast cancer about 25 % to 30 % among women aged 50 to 69 years after only five to six years from the initiation of screening. Among women aged 40 to 49 years, trials have reported no reduction in breast cancer mortality after seven to nine years from the initiation of screening; after 10 to 14 years there is a 16% reduction in breast cancer mortality. Given that the inci-dence of breast cancer for women aged 40 to 49 years is lower and the potential benefit from mammography screen-ing smaller and delayed, the absolute number of deaths pre-vented by screening women aged 40 to 49 years is much less than in screening women aged 50 to 69 years. Because the absolute benefit of screening women aged 40 to 49 years is small and there is concern that the harms are substantial, the focus should be to help these women make informed deci-sions about screening mammography by educating them of their true risk of breast cancer and the potential benefits and risks of screening. [Monogr Natl Cancer Inst 1997;22:79–86] Most experts agree that women aged 50 to 69 years should undergo screening mammography, since randomized controlled trials have shown screening mammography to reduce breast can-cer mortality (1,2) and to be relatively cost-effective (3,4) for women in this age group. Whether or not recommendations should be extended to include screening starting at age 40 years remains controversial (5–9). This controversy stems from dif-ferences in interpretation of evidence and type of evidence used to evaluate whether screening mammography is efficacious