August 05, 2013
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Long-term use of calcium-channel blockers may raise breast cancer risk

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Use of calcium-channel blockers for 10 years or more was associated with higher risk for ductal breast cancer and lobular breast cancer, according to findings from a large, population-based, case-control study.

Christopher I. Li, MD, PhD, and colleagues observed no link between breast cancer and other classes of antihypertensive medications.

“Our results do suggest that long-term current use of calcium-channel blockers is associated with an increased risk of both [invasive ductal carcinoma] and [invasive lobular carcinoma] and that these associations do not vary according to [estrogen receptor] status,” Li, of the division of public health sciences at the Fred Hutchinson Cancer Research Center, Seattle, and colleagues wrote.

Previous studies exploring the relationship between antihypertensive medications and breast cancer returned inconsistent findings, according to the study background. Most studies were small, with the largest ones dating back to the 1990s, and were unable to assess the impact of long-term medication use, the researchers wrote.

The study included women aged 55 to 74 years from the Seattle metropolitan area who had no prior history of cancer and were diagnosed with a primary invasive breast cancer between January 2000 and December 2008. They interviewed 916 patients with ductal breast cancer, 1,068 patients with lobular breast cancer and 902 women from a control group. All women were asked about their history of hypertension, CVD and use of antihypertensive medications. Medication classes discussed included ACE inhibitors, angiotensin receptor blockers, beta-blockers, calcium-channel blockers (CCBs), diuretics and combination preparations.

The researchers found no association between either type of breast cancer and use of any class of antihypertensive medication for less than 10 years. However, there was an association between current use of CCBs for ≥10 years and increased risk for ductal breast cancer (OR=2.4; 95% CI, 1.2-4.9) and lobular breast cancer (OR=2.6; 95% CI, 1.3-5.3). No other antihypertensive medication classes were associated with either type of breast cancer when used for ≥10 years.

Further research is needed “to confirm this finding and to evaluate potential underlying biological mechanisms,” Li and colleagues wrote.

In a related editorial, Patricia F. Coogan, ScD, of Slone Epidemiology Center at Boston University, called the study “first-rate” because of its size, high response rate and use of best practices in determining participants’ current and prior medication use. She said bias from confounding by indication was unlikely because the researchers conducted a subanalysis of the participants who reported a history of hypertension. She also said that recall bias was unlikely because it would likely have extended to all medication classes in the survey.

However, Coogan said, more research must be done before clinical practice is changed. “Given these results, should the use of CCBs be discontinued after 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 clinical practice,” she wrote. “Should the results be dismissed as random noise emanating from an observational study? The answer is no, because the data make a convincing case that the hypothesis that long-term CCB use increases the risk for breast cancer is worthy of being pursued.”

For more information:

Coogan PF. JAMA Intern Med. 2013;doi:jamainternmed.2013.9069.

Li CI. JAMA Intern Med. 2013;doi:10.1001/jamainternmed.2013.9071.

Disclosure: Coogan and the researchers report no relevant financial disclosures.