Abstract
BACKGROUND: The authors previously reported that within a patient cohort from Victoria, Australia, women who had early-stage breast cancer (ESBC) diagnosed while participating in screening [active screeners (AS), comprising both screen-detected and interval cancers] receive less intensive treatment than those not recently screened (NRS). This study reports mortality and subsequent cancer events for that cohort. METHODS: Follow-up data were collected for 766 (97.1%) of the 789 women in the original cohort (612 [79.9%] AS and 154 [20.1%] NRS), with a median follow-up time of 11.6 years (interquartile range [IQR], 9.8-13.8 years). Mortality and subsequent cancer diagnosis data were derived from linkage with the Victorian Cancer Registry. Breast cancer-specific survival (BCSS) and overall survival (OS) were compared between groups, with sensitivity analyses for potential overdiagnosis and lead time bias. RESULTS: The 10-years BCSS was 95.4% (95% confidence interval [CI], 93.2-96.8%) for AS versus 86.4% (95% CI 79.7-91.0%) for NRS (hazard ratio [HR], 0.28; 95% CI 0.17-0.48; p < 0.001). A survival benefit persisted after adjustment for estimated overdiagnosis (HR 0.38; 95% CI 0.21-0.66; p = 0.001) and lead time bias (HR 0.33; 95% CI 0.19-0.58; p < 0.001). The 10-year OS also was superior for AS, at 90.6% (95% CI 87.9-92.7%) compared with 82.5% (95% CI 75.4-87.8%) for NRS (HR 0.54; 95% CI 0.36-0.79; p = 0.002). DISCUSSION: Patients who have ESBC diagnosed while participating in screening experience improved BCSS and OS while receiving less intensive treatment. These findings are robust to adjustment for potential overdiagnosis and lead time bias. As treatment for ESBC becomes more tailored, with emerging opportunities for reduced treatment intensity, the benefits of screening are likely to improve further.