Background: Previous studies have been interpreted as suggesting an increase in risk of cancer among users of calcium-channel blockers compared with users of beta-blockers. To explore this issue further, we studied a large group of hypertensive patients to investigate the relation of calcium-channel blockers and cancer.
Methods: In cohorts of users of calcium-channel blockers, angiotensin-converting-enzyme (ACE) inhibitors, and beta-blockers, we identified all cases of cancer diagnosed in 1995. We used a nested case-control analysis to estimate the risk of cancer among users of calcium-channel blockers and ACE inhibitors, with users of beta-blockers as a reference group. The study was based on information taken from the General Practice Research Database, and the study population was restricted to patients with at least 4 years of medical history recorded on computer.
Findings: The study was based on 446 cases of cancer and 1750 controls. The relative risk estimates for all cancers combined were 1.27 (95% CI 0.98-1.63) and 0.79 (0.58-1.06) for users of calcium-channel blockers and ACE inhibitors, respectively, relative to users of beta-blockers. There was little difference in risk estimates with duration of use of calcium-channel blockers of less than 1.0 year (relative risk 1.46), 1.0-3.9 years (1.26), and 4.0 years or more (1.23).
Interpretation: The small positive association between calcium-channel blockers and risk of cancer is unlikely to be causal since there is no increase in risk with increasing duration of calcium-channel blocker use.