Cancer risk of hypertensive patients taking calcium antagonists.

OBJECTIVE: To measure rates of incident and fatal cancer in hypertensive patients taking calcium antagonists and to compare these with rates in three control groups. DESIGN: A retrospective analysis of cancer in patients of the Glasgow Blood Pressure Clinic prescribed either a calcium antagonist or other antihypertensive drugs (non-calcium antagonist group). Record linkage of the clinic with the West of Scotland Cancer Registry and with the Registrar General, Scotland provided information on incidence of cancer and on deaths and their causes. PATIENTS: 2297 patients were prescribed calcium antagonist and 2910 were prescribed antihypertensive drugs other than calcium antagonist. MAIN OUTCOME MEASURES: Relative risk of cancer, the ratio of observed to expected cancers in the calcium antagonist group, was estimated using expected values based on three control groups; namely the non-calcium antagonist group, a middle-aged population of Renfrew and Paisley and the West of Scotland population. RESULTS: There were 134 incident cancers in the calcium antagonist group, representing relative risks of 1.02 [95% confidence interval (CI) 0.82-1.271 compared with the non-calcium antagonist group, 1.01 (95% CI 0.84-1.18) compared with Renfrew-Paisley controls and 1.02 (95% CI 0.85-1.19) compared with West of Scotland controls. Findings for cancer mortality were similarly negative. Risks were no higher for older patients. CONCLUSIONS: Our study lends no support to the suggestion that calcium antagonists cause cancer.