Commentary: Association Between Antihypertensive Medication Use and Breast Cancer: A Systematic Review and Meta-Analysis

Introduction

In an emerging age of precision medicine, clarity on the impact of concomitant non-cancer medicines on the efficacy of anti-cancer treatments has never been so important. For example, immunotherapies are emerging as an important treatment option in breast cancer (e.g., atezolizumab, pembrolizumab) (Schmid et al., 2018; Cescon et al., 2020). Further, it is hypothesised that concomitant medicines such as beta-blockers, statins, and metformin may boost immunotherapy actions (Kokolus et al., 2017; Afzal et al., 2018; Cortellini et al., 2020), while antibiotics and proton pump inhibitors may impair responses (Hopkins et al., 2020a; Hopkins et al., 2020b; Cortellini et al., 2020). However, undertaking randomised control trials to identify the impact of each non-cancer concomitant medicine on breast cancer prognosis is not practicable due to cost, exposure to potentially harmful strategies, and years until results become apparent. Thus, we read with great interest the systematic review and meta-analysis from Xie et al. on the association between concomitant antihypertensive medication use and breast cancer risk and prognosis (breast cancer-specific mortality, recurrence, overall survival, and disease-specific survival) (Xie et al., 2021). Xie et al. (2021) concluded that the use of calcium channel blockers, beta-blockers, or diuretics was significantly associated with an increased risk of developing breast cancer, and that diuretic use may elevate the risk of breast cancer-specific mortality (with no statistically significant association found for calcium channel blockers, beta-blockers, or renin-angiotensin system inhibitors). Underlying assumptions of these conclusions are that the meta-analysis strategy acquired sufficient power to assess the associations and the author team adequately evaluated and filtered original scientific literature for quality. In relation to this evaluation, we appreciate the scoring system used by the authors to differentiate the quality of prior studies, however greater detail on the specifics of each study achieving their score would be appreciated.