The Use of Antihypertensive Medication and the Risk of Breast Cancer in a Case-Control Study in a Spanish Population: The MCC-Spain Study

INTRODUCTION: The evidence on the relationship between breast cancer and different types of antihypertensive drugs taken for at least 5 years is limited and inconsistent. Furthermore, the debate has recently been fueled again with new data reporting an increased risk of breast cancer among women with a long history of use of antihypertensive drugs compared with nonusers. METHODS: In this case-control study, we report the antihypertensive drugs–breast cancer relationship in 1,736 breast cancer cases and 1,895 healthy controls; results are reported stratifying by the women’s characteristics (i.e., menopausal status or body mass index category) tumor characteristics and length of use of antihypertensive drugs. RESULTS: The relationship among breast cancer and use of calcium channel blockers (CCB) for 5 or more years had odds ratio (OR) = 1.77 (95% CI, 0.99 to 3.17). Stratifying by BMI, the OR increased significantly in the group with BMI ≥ 25 (OR 2.54, 95% CI, 1.24 to 5.22). CCBs were even more strongly associated with more aggressive tumors, (OR for invasive tumors = 1.96, 95% CI = 1.09 to 3.53; OR for non ductal cancers = 3.97, 95% CI = 1.73 to 9.05; OR for Erbb2+ cancer = 2.97, 95% CI: 1.20 to 7.32). On the other hand, premenopausal women were the only group in which angiotensin II receptor blockers may be associated with breast cancer (OR = 4.27, 95% CI = 1.32 to 13.84) but this could not be identified with any type or stage. Use of angiotensin-converting-enzyme inhibitors, beta blockers and diuretics were not associated with risk. CONCLUSIONS: In this large population-based study we found that long term use of calcium channel blockers is associated with some subtypes of breast cancer (and with breast cancer in overweight women).