Screening Women Aged 40-49 Years: Where Are We Today?

Abstract

The fact that mammographic screening can reduce deaths from breast cancer is well established and is unarguably true for women aged 50-69 years (12)- While the unique value of mammography in the early detection of breast cancer is also well established, it is less certain if early detection results in similar mortality reductions for women diagnosed with breast cancer between the ages of 40 and 49 years compared with women aged 50 years and older. This uncertainty is, at the outset, the result of an inadequate base of scientific data. Specifically, no trial to date, with the exception of the Canadian National Breast Screening Study (NBSS-1), was designed to have adequate statistical power to test the hypothesis of a benefit from mammography for women aged 40^9 years, and the results are not universally accepted due to concerns about study methodology. While the majority of these trials suggest a benefit for women aged 40-49 years, none of the observed mortality differences in individual studies has achieved conventional criteria for statistical significance (3). Periodic updates of trial data have been published, but small sample sizes in individual studies remain a limiting factor. However, there are other limiting factors that potentially influence trial results, and these factors may have been especially influential on outcomes for women aged 40-49 years. These factors include mammographic technique, one versus two views, and the interval between screenings. To address the limitations of small sample sizes and these quality-assurance