Comparing screening mammography for early breast cancer detection in Vermont and Norway

Abstract

Background: Most screening mammography in the United States differs from that in countries with formal screening programs by having a shorter screening interval and interpretation by a single reader vs independent double reading. We examined how these differences affect early detection of breast cancer by comparing performance measures and histopathologic outcomes in women undergoing opportunistic screening in Vermont and organized screening in Norway. Methods: We evaluated recall, screen detection, and interval cancer rates and prognostic tumor characteristics for women aged 50-69 years who underwent screening mammography in Vermont (n = 45 050) and in Norway (n = 194 430) from 1997 through 2003. Rates were directly adjusted for age by weighting the rates within 5-year age intervals to reflect the age distribution in the combined data and were compared using two-sided Z tests. Results: The age-adjusted recall rate was 9.8% in Vermont and 2.7% in Norway (P