Population-based cohort study of post-diagnostic beta blocker use and breast cancer-specific mortality

Many patients with breast cancer use prescribed medications for cardiovascular conditions. Studies of the association of beta blocker (BB) use and breast cancer-specific mortality (BCD) have yielded contradictory results. A population-based study in New Zealand included almost 15,000 women with a first diagnosis of breast cancer and median follow-up of 4.51 years. Twenty-one percent used BBs after diagnosis. BB use was associated with a statistically significant increased BCD risk confined to short-term use (0-3 months; HR 1.40; 95% CI 1.14-1.73). The risk steadily decreased with increasing duration of use, and became a statistically protective effect at 3+ years of use (HR 0.55; 95% CI 0.34-0.88).