A new study has reported that use of beta blockers and ACE inhibitors (angiotensin-converting enzyme inhibitors) might influence risk of breast cancer recurrence. Both drugs are used to treat cardiovascular conditions such as hypertension and heart failure. Like certain behavioral factors and concurrent medical conditions, use of non-cancer-related prescription drugs may affect breast cancer outcome.

To conduct the study, the authors used data from the Life After Cancer Epidemiology (LACE) Study, which included 1,779 women with early stage breast cancer enrolled in the Kaiser Permanente Northern California Cancer Registry. The associations between beta blockers and/or ACE inhibitors and breast cancer recurrence, breast cancer-specific death, and death from any cause (overall mortality) were calculated.

A total of 292 breast cancer recurrences, 174 breast cancer deaths, and 323 deaths from all causes were observed in the study group. 23% of the women used a beta blocker and/or an ACE inhibitor. Women taking these drugs tended to be older and postmenopausal, with greater pre-diagnosis body mass index (BMI), and more likelihood of high blood pressure and type 2 diabetes. They were also more likely to be using tamoxifen. Use of ACE inhibitors was found to be associated with a 56% increased risk of breast cancer recurrence, but not with breast cancer-specific death or overall mortality. On the other hand, using beta blockers was associated with lower risk of recurrence and breast cancer-specific mortality. However, no evidence of a dose response was found for either medication, a fact which undermines any argument for causality. Using both an ACE inhibitor and a beta blocker at the same time was found to be associated with increased overall mortality than not using either drug. However, combining a beta blocker with an ACE inhibitor was linked to lower risks of breast cancer recurrence and breast cancer-specific mortality than when an ACE inhibitor was used alone. The authors conclude that these preliminary findings, which need to be confirmed, suggest that breast cancer recurrence and survival are influenced by exposure to two commonly used classes of anti-hypertensive medications. The study observations suggest that greater attention should focus on the potential role of these commonly used medications in breast cancer outcomes.