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June 17, 2015
Calcium-Channel Blockers Might Not Raise Breast Cancer
Risk After All

Chicago—A 2013 population-based case-control study in the Seattle area found that long-term current use of calcium-channel blockers (CCBs) appeared to increase breast cancer risk, raising concerns and likely resulting in many women changing their blood pressure–lowering medications.

A new long-term study, presented recently at the American Society of Clinical Oncology’s annual meeting in Chicago, found no association, however, between use of CCBs and increased risk of developing breast cancer.

Calling the association of CCBs and breast cancer risk “controversial,” authors of the recently presented study said they sought to determine if a link existed and whether cumulative duration of use makes a difference. The study was led by researchers from McGill University in Montreal.

To do that, the Canadian researchers used a United Kingdom database, the Clinical Practice Research Datalink, to examine a cohort of 273,152 women newly treated with antihypertensive drugs between January 1, 1995 and December 31, 2009, following them until December 31, 2010.

All models were adjusted for a number of potential confounders, including age, smoking status, body mass index, alcohol consumption, and use of hormone replacement therapy or other prescription drugs.

Results indicate that during 1,567,104 person-years of follow-up, 4,520 women were newly diagnosed with breast cancer with an incidence rate of 2.9 per 1,000 per year.

Yet, compared with other antihypertensive drugs, the use of CCBs was not associated with an increased risk of breast cancer, 2.8 versus 3.1 per 1,000 per year, respectively. The 2013 study had found use of diuretics, beta-blockers, and angiotensin II antagonists were not associated with greater risks, while CCBs were.

The secondary analysis in the recent study found, meanwhile, that the risk did not vary significantly according to cumulative duration of use. The rate of breast cancer per 1,000 per year ranged from 0.97 at less than 5 years to 0.94 to 1.25 at 10 years or longer.

“The results of this large population-based study indicate that the long-term use of CCBs is not associated with an increased risk of breast cancer,” the authors conclude.
U.S. Pharmacist Social Connect