Calcium Channel Blockers and the Risk of Cancer

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Abstract
IN 1996, Pahor et al1,2 raised the concern that calcium channel blockers (CCBs) may be carcinogenic. After 3.7 years of follow-up of 5052 people, they found a statistically significant 1.72-fold increase in the overall risk of cancer among persons who used CCBs, based on 47 cancers that occurred among users and 373 among nonusers. Elevations in risk greater than 1.5-fold were observed for cancers of the bladder, ureter, or kidney; breast; colon; prostate; lymphatic or hemopoietic system; stomach; and uterus. Results from subsequent studies have been mixed. A case-control study reported by Jick et al,3 which included 446 cases of cancer and which had more complete data on drug exposure, did not support a material effect of CCB use on cancer risk overall: the relative risk (RR) estimate was 1.27 (95% confidence interval [CI], 0.98-1.63) in CCB users relative to users of β-blockers, and the risk did not increase with increasing duration of use. Relative risk estimates were not elevated for the individual cancers for which risk was elevated in the study of Pahor et al,1 but numbers were small. In a Danish follow-up study of 17911 patients who had received at least 1 prescription for a CCB, the incidence of cancer was not increased after up to 3 years of follow-up: 412 cancers occurred, whereas 414 were expected on the basis of national incidence rates.4 An association between CCB use and increased risk of breast cancer was reported from a study of 3198 women who had been followed up for up to 5 years.5 Based on 20 cases of breast cancer among women who had used CCBs and 55 cases among women who had not, the hazard ratio was 2.57 (95% CI, 1.47-4.49).