SEER Medicare database analysis of association of screening history with stage at diagnosis and mortality in screen-detected breast cancer

Screening mammography promotes early detection of breast cancer and is associated with reduced breast cancer mortality. Screening history prior to diagnosis may impact stage at diagnosis and breast cancer mortality but has not been comprehensively examined within a diverse US cohort. A cohort study using the SEER Medicare database included 13.028 women aged 70 years or older with screen-detected ER-positive or HER2-negative breast cancer. Among these, 3812 women (29.3%) were diagnosed with later-stage disease (T2+ or N1+) at the time of diagnosis. In multivariable analysis, prior screening was associated with 54% lower odds of later-stage breast cancer (aOR 0,46; 95% CI 0.42-0.60) and 37% lower odds of breast cancer-specific death (aHR 0.63; 95% CI 0,52-0,76) compared with no prior screening. Having 3 or 4 prior screenings was assocatied with 37% reduced hazard of breast cancer-specific mortality compared with having 1 prior screening (aHR 0.63; 95% CI 0.44-0.89). The authors conclude that prior screening was associated with more favorable stage and mortality; however the extent to which this reflects a true benefit of screening remains unclear due to poential selection bias.