Background: It is unclear if use of common antihypertensive medications influences the risk of adverse breast cancer outcomes.Methods: Using the linked Surveillance, Epidemiology and End-Results (SEER)-Medicare database, we identified 14,766 women between ages 66 and 80 years diagnosed with incident stage I/II breast cancer between 2007 and 2011. Medicare Part D data were obtained to characterize women's post-cancer use of various antihypertensive medications. Outcomes included a second breast cancer event (SBCE; a composite outcome defined as the first of a recurrence or a second contralateral primary breast cancer), breast cancer recurrence, and breast cancer-specific mortality. Time-varying Cox proportional hazard models were used to estimate hazard ratios (HR) and their associated 95% confidence intervals (CI).Results: There were 791 SBCEs, 627 breast cancer recurrences, and 237 breast cancer deaths identified over a median follow-up of 3 years. Use of diuretics (n = 8,517) after breast cancer diagnosis was associated with 29% (95% CI, 1.10-1.51), 36% (95% CI, 1.14-1.63) and 51% (95% CI, 1.11-2.04) higher risks of a SBCE, recurrence, and breast cancer death, respectively. Compared with nonusers, β-blockers users (n = 7,145) had a 41% (95% CI, 1.07-1.84) higher risk of breast cancer death. Use of angiotensin II receptor blockers, calcium channel blockers and angiotensin-converting enzyme inhibitors were not associated with risks of breast cancer outcomes.Conclusions: Use of diuretics and β-blockers may be associated with increased risk of breast cancer outcomes among older women.Impact: Most antihypertensive medications are safe with respect to breast cancer outcomes, but more research is needed for diuretics and β-blockers. Cancer Epidemiol Biomarkers Prev; 26(11); 1603-10. ©2017 AACR.
©2017 American Association for Cancer Research.