Calcium-channel blockers and risk of cancer

Background Previous studies have been interpreted as suggesting an increase in risk of cancer among users of calcium-channel blockers compared with users of β-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 β-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 β-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 β-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.