Long-term use of calcium-channel blocker for hypertension associated with higher breast cancer risk

Long-term use of a calcium-channel blocker for hypertension was associated with about a 2.5 times higher risk of breast cancer, according to a study.

Researchers conducted a population-based study among women ages 55 to 74 years in the three-county Seattle-Puget Sound metropolitan area. There were 880 women who had invasive ductal breast cancer, 1,027 who had invasive lobular breast cancer, and a control group of 856 who did not have cancer.

Results appeared online Aug. 5 in JAMA Internal Medicine.

Overall, antihypertensives were not associated with increased risk of either kind of breast cancer. However, current use of calcium-channel blockers for 10 or more years was associated with higher risks of both invasive ductal carcinoma (odds ratio [OR], 2.4; 95% CI, 1.2 to 4.9) and invasive lobular carcinoma (OR, 2.6; 95% CI, 1.3 to 5.3).

The study found that short-acting calcium-channel blockers might be particularly associated with cancer risk. Current users of short-acting calcium-channel blockers had an increased risk of invasive ductal carcinoma (OR, 3.7; 95% CI, 1.2 to 11.8) and a similar increased risk of invasive lobular carcinoma (OR, 3.6; 95% CI, 1.2 to 11.4) compared to non-users.

Current use of long-acting calcium-channel blockers was not associated with increased risk of either cancer, but the subgroup using them for 10 years or longer had elevated risks of invasive ductal carcinoma (OR, 2.7; 95% CI, 1.2 to 5.7) and invasive lobular carcinoma (OR, 2.5; 95% CI, 1.2 to 5.5). For short-acting agents, the effect of duration of use could not be assessed due to lack of power.

Current use of non-dihydropyridines for any duration was associated with a 60% increased risk of both invasive ductal carcinoma and invasive lobular carcinoma, but researchers noted that the risk estimate for invasive ductal carcinoma was within the limits of chance. Current use of dihydropyridines for 10 years or longer was associated with elevated risks of invasive ductal carcinoma (OR, 3.0; 95% CI, 1.0 to 8.9) and invasive lobular carcinoma (OR, 3.4; 95% CI, 1.1 to 9.9). Diuretics, β-blockers and angiotensin II antagonists were not associated with increased breast cancer risk.

“While some studies have suggested a positive association between calcium-channel blocker use and breast cancer risk, this is the first study to observe that long-term current use of calcium-channel blockers in particular are associated with breast cancer risk,” the study concluded.

An editorial noted that study made a “convincing case” that long-term use of calcium-channel blockers increases the risk of breast cancer and should be followed up. Calcium-channel blockers were the ninth most commonly prescribed class of drugs in the U.S. in 2009, and breast cancer is the most commonly occurring cancer among women. An association that is confirmed between the two would make calcium-channel blockers a major modifiable risk factor.

However, the editorial cautioned, “Given these results, should the use of CCBs [calcium-channel blockers] be discontinued once a patient has taken them for 9.9 years? The answer is no, because these data are from an observational study, which cannot prove causality and by itself cannot make a case for change in clinical practice.”