Critically Assessing Risks and Benefits of Screening Mammography

Screening mammography is based on the premise that detecting small, nonpalpable tumors can lower incidence of larger tumors. To assess screening mammography's effects on overdiagnosis (detection of tumors that will not lead to symptoms) and breast cancer mortality, investigators analyzed population-based cancer registry data in women aged ≥40 (representing about 10% of the U.S. population), with a focus on tumor size. Data from 1975 to 1979 (prior to widespread screening) and 2000 to 2002 (the most recent period for which 10-year follow-up data were available) were compared.

With the advent of widespread screening, incidence of small (<2 cm) in situ and invasive breast tumors increased by 162 cases per 100,000 women, whereas incidence of lar…