Reduction in late-stage breast cancer incidence in the mammography era: Implications for overdiagnosis of invasive cancer.

Abstract

Mammographic screening is expected to decrease the incidence of late-stage breast cancer. In the current study, the authors determined the decrease in late-stage cancer incidence and the changes in invasive cancer incidence that occurred in the mammographic era after adjusting for prescreening temporal trends. Breast cancer incidence and stage data were obtained from the Surveillance, Epidemiology, and End Results program. The premammography period (1977-1979) was compared with the mammographic screening period (2007-2009) for women aged ≥ 40 years. The authors estimated prescreening temporal trends using 5 measures of annual percentage change (APC). Stage-specific incidence values from 1977 through 1979 (baseline) were adjusted using APC values of 0.5%, 1.0%, 1.3%, and 2.0% and then compared with observed stage-specific incidence in 2007 through 2009. Prescreening APC temporal trend estimates ranged from 0.8% to 2.3%. The joinpoint estimate of 1.3% for women aged ≥ 40 years approximated the 4-decade long APC trend of 1.2% noted in the Connecticut Tumor Registry. At an APC of 1.3%, late-stage breast cancer incidence decreased by 37% (56 cases per 100,000 women) with a reciprocal increase in early-stage rates noted from 1977 through 1979 to 2007 through 2009. Resulting late-stage cancer incidence decreased from 21% at an APC of 0.5% to 48% at an APC of 2.0%. Total invasive breast cancer incidence decreased by 9% (27 cases per 100,000 women) at an APC of 1.3%. There is evidence that a substantial reduction in late-stage breast cancer has occurred in the mammography era when appropriate adjustments are made for prescreening temporal trends. At background APC estimates of ≥ 1%, the total invasive breast cancer incidence also decreased.