Post-Diagnostic Beta Blocker Use and Breast Cancer-Specific Mortality: A Population-Based Cohort Study

Abstract

Purpose Beta blockers (BB) have been associated with improved, worsened, or unchanged breast cancer outcomes in previous studies. This study examines the association between the post-diagnostic use of BBs and death from breast cancer in a large, representative sample of New Zealand (NZ) women with breast cancer. Methods Women diagnosed with a first primary breast cancer between 2007 and 2016 were identified from four population-based regional NZ breast cancer registries and linked to national pharmaceutical data, hospital discharges, and death records. The median follow up time was 4.51 years. Cox proportional hazard models were used to estimate the hazard of breast cancer-specific death (BCD) associated with post-diagnostic BB use. Results Of the 14,976 women included in analyses, 21% used a BB after diagnosis. BB use (vs non-use) was associated with a small and non-statistically significant increased risk of BCD ( adjusted hazard ratio: 1.11; 95% CI: 0.95-1.29). A statistically significant increased risk confined to short-term use (0-3 months) was seen (HR=1.40; 1.14-1.73), and this risk steadily decreased with increasing duration of use and became a statistically significant protective effect at 3+ years of use (HR=0.54; 0.34-0.87). Conclusion Our findings suggest that any increased risk associated with BB use may be driven by risk in the initial few months of use. Long-term BB use may be associated with a reduction in BCD.