Use of calcium channel blockers and risk of breast cancer among women aged 55 years and older: a nationwide population-based cohort study.

This retrospective cohort study was aimed to compare the incidence of breast cancer among women aged ≥55 who received calcium channel blockers and angiotensin converting enzyme inhibitors/angiotensin II receptor blockers. We used the 2002-2015 Health and Welfare Database in Taiwan. Women 55 years and older who initiated antihypertensive treatment were included. Breast cancer risk for patients receiving calcium channel blockers was compared to those receiving angiotensin converting enzyme inhibitors/angiotensin II receptor blockers. Cox proportional hazards models were used to generate adjusted hazard ratios for breast cancer. We found that the risk of breast cancer was similar between calcium channel blockers users and angiotensin converting enzyme inhibitors/angiotensin II receptor blockers (adjusted hazard ratio [aHR] and 95% CI = 1.03 [0.80 to 1.34]). No significant risk increase was observed in the stratified analysis by dihydropyridine (aHR = 1.02 [0.78 to 1.33]) and non-dihydropyridine calcium channel blockers (aHR = 1.23 [0.48 to 3.20]). No difference in the risk of breast cancer associated with calcium channel blockers exposure was observed in patients who used hormone replacement therapy (aHR = 1.02 [0.29 to 3.58]). The risk for breast cancer was observed to be significantly lower in patients receiving calcium channel blockers than in those receiving angiotensin converting enzyme inhibitors/angiotensin II receptor blockers at a treatment duration of 5 or more years (aHR = 0.57 [0.33 to 0.98]). In conclusion, the risk for breast cancer is similar for calcium channel blockers and angiotensin converting enzyme inhibitors/angiotensin II receptor blocker users in an Asian population.