(HealthDay News) — For postmenopausal women, long-term use of calcium-channel blockers may be associated with an increased risk of invasive ductal and lobular breast cancer, according to a study published online Aug. 5 in JAMA Internal Medicine.

Christopher I. Li, M.D., Ph.D., from the Fred Hutchinson Cancer Research Center in Seattle, and colleagues conducted a population-based case-control study to examine the correlation between various classes of antihypertensive medications and the risks of invasive ductal and invasive lobular breast cancers. Participants included postmenopausal women aged 55 to 74 years with invasive ductal breast cancer (880 women), invasive lobular breast cancer (1,027 women), and 856 controls with no cancer.

The researchers found that the risk of ductal breast cancer and lobular breast cancer correlated significantly with current use of calcium-channel blockers for 10 or more years (odds ratio, 2.4 and 2.6, respectively). There was no appreciable variation in the correlation with the type of calcium-channel blocker used. No correlation with risk was seen for use of diuretics, β-blockers, or angiotensin II antagonists.

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“In summary, this study provides evidence that long-term recent use of calcium-channel blockers may be associated with an increased risk of breast cancer,” the authors write. “Further efforts to confirm this association are needed and are of public health importance, given that antihypertensive drugs are the most commonly prescribed class of medication in the United States.”