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In this issue of JAMA Internal Medicine, a report by Li et al1 from a large population-based case-control study suggests that long-term use of calcium-channel blockers (CCBs) is associated with a greater than 2-fold increase in the risk of breast cancer in postmenopausal women. This is not the first time that the specter of CCB-associated cancer has arisen: in 1996, Pahor et al2 reported a statistically significant 72% increase in risk of all cancers among CCB users in an elderly cohort, including a nonsignificant 65% increased risk of breast cancer. This was followed in 1997 by a report from another elderly cohort of a statistically significant relative risk (RR) for breast cancer of 2.6 among ever users of CCBs.3 Both studies were based on small numbers. Subsequent larger case-control and cohort studies failed to confirm the CCB-cancer association for all cancers4 or for breast cancer,5 nor did excess cancers occur in up to 5 years of follow-up in 3 randomized clinical trials of CCBs.6- 8 The CCB-cancer hypothesis went into hibernation.
Coogan PF. Calcium-Channel Blockers and Breast CancerA Hypothesis Revived. JAMA Intern Med. 2013;173(17):1637-1638. doi:10.1001/jamainternmed.2013.9069