Examining the influence of beta blockers and ACE inhibitors on the risk for breast cancer recurrence: results from the LACE cohort

There is increasing interest in the relationship between host lifestyle factors and the outcomes of cancer treatment. Behavioral factors, comorbid conditions, and non-cancer-related pharmaceutical exposures may affect breast cancer (BC) outcomes. We used observational data from the LACE Study cohort (women with early stage BC from the Kaiser Permanente Northern California Cancer Registry) to examine the association between beta blockers (BBs) and/or angiotensin-converting enzyme inhibitors (ACEi) and BC recurrence, BC-specific mortality, and overall mortality. Among 1,779 women, there were 292 BC recurrences, 174 BC deaths, and 323 total deaths. 23% were exposed to either a BB and/or an ACEi. These drugs were associated with older age, postmenopausal status, tamoxifen therapy, greater pre-diagnosis BMI, hypertension, and diabetes. In Cox proportional hazards models, ACEi exposure was associated with BC recurrence (HR 1.56, 95% CI 1.02, 2.39, P = 0.04), but not cause-specific or overall mortality. Combined ACEi and BB were associated with overall mortality (HR 1.94, 95% CI 1.22, 3.10, P = 0.01). BB exposure was associated with lower hazard of recurrence and cause-specific mortality. However, there was no evidence of a dose response with either medication. For recurrence and cause-specific mortality, BB combined with ACEi was associated with a lower HR for the outcome than when ACEi alone was used. These hypothesis generating findings suggest that BC recurrence and survival were associated with exposure to two commonly used classes of anti-hypertensive medications. These observations need to be confirmed and suggest that greater attention should focus on the potential role of these commonly used medications in BC outcomes.