Rationale for Annual Screening Mammography for Women Ages 40–49 Years

Proof of the benefit for mammographic screening of women ages 40–49 years is now available. Randomized controlled trials (RCTs) conducted in Gothenburg and Malmo, Sweden have shown statistically significant breast cancer mortality reductions of 36% and 45% respectively. A meta-analysis of all five Swedish trials has found a statistically significant mortality reduction of 29% for woman in this age group. Substantially greater reductions in mortality would likely have resulted if women in these trials had been screened annually. Because the benefits are substantial, and the risks from screening are relatively small and acceptable, screening mammography beginning at age 40 is now recommended by the American Cancer Society, as well as the National Cancer Institute.