Calcium channel blockers and breast cancer incidence: An updated systematic review and meta-analysis of the evidence.

Controversy exists regarding the potential association between taking calcium channel blockers (CCBs) and the development of breast cancer. As a positive association would have important public health implications due to the widespread use of CCBs, this study aimed to incorporate new evidence to determine whether an association is likely to exist. We searched MEDLINE, EMBASE and the Cochrane Library to 28 June 2016 for relevant literature. References and citing articles were checked and authors contacted as necessary. Two authors independently selected articles and extracted data. Twenty-nine studies were reviewed; 26 were non-randomised studies (NRS). Meta-analysis of study data where adjustment for 'confounding by indication' was judged to be present suggests that an association, if any, is likely to be modest in magnitude (pooled odds/risk ratio 1.09 (95% confidence interval (CI) 1.03-1.15, I