August 14, 2013
Extended Use of Calcium-Channel Blockers Linked to
Increase in Breast Cancer

Seattle, WA—Women who use calcium-channel blockers over the long term increased their breast cancer risk, according to a recent study that reported that the effect was not seen with other types of antihypertensives—diuretics, beta-blockers, and angiotensin II antagonists.

The report, published recently in JAMA Internal Medicine, said that current use of calcium-channel blockers for 10 or more years was associated with higher risks of ductal breast cancer (odds ratio [OR], 2.4) and lobular breast cancer (OR, 2.6), adding that the link to increased breast cancer risk showed little variation whether the medication was short-acting or long-acting or whether dihydropyridines or nondihydropyridines were used.
Background in the article, which was funded by the National Cancer Institute and the U.S. Department of Defense, notes that an estimated 678 million prescriptions for antihypertensive medications were filled in the United States in 2010.

“Because hypertension is a chronic condition, most people with high blood pressure use antihypertensive drugs chronically and will often stay on the same regimen for long periods of time,” said lead author Christopher I. Li, MD, PhD, of the Fred Hutchinson Cancer Research Center in Seattle. “Characterizing their potential associations with the most common cancer in women is an important clinical and public health issue, particularly with the increasing availability of alternative options to manage hypertension.”

Conducted in the three-county Seattle-Puget Sound metropolitan area, the population-based study included women ages 55 to 74 years: 880 of the women had invasive ductal breast cancer, 1,027 had invasive lobular breast cancer, and 856 of them had no cancer and served as the control group. Interviewing participants in person, researchers gathered in-depth histories of hypertension and heart disease, as well as risk factors for cancer, including family history, obesity, smoking, and alcohol use. Through a series of structured questions, the research also included detailed data regarding use of antihypertensive drugs, such as beginning and end dates of use, drug names, dose, route of administration, pattern of use, and indication.

Results suggested that women currently taking calcium-channel blockers who have used them for a decade or longer had an approximately two and a half times higher risk of both invasive ductal and invasive lobular cancers, compared to those who never used such calcium-channel blockers or to users of other forms of antihypertensives.
The antihypertension drug classes have “different potential benefits as well as side effects,” Li said. “Choice of which regimen a patient is given depends on their tolerance of medication, other conditions, and whether their hypertension can be managed by a single drug or requires a combination of drugs.”

Study authors note that, while past research has “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. Additional research is needed to confirm this finding and to evaluate potential underlying biological mechanisms,” the study concludes.

In an invited commentary, Patricia F. Coogan, ScD, of the Slone Epidemiology Center at Boston University, notes that the study “has significant clinical and public health implications,” but does not recommend a change in prescription practices at this point.

“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,” Coogan says, adding, “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 of breast cancer is worthy of being pursued.”

U.S. Pharmacist Social Connect