Long-term diuretic therapy in patients with coronary disease: Increased colon cancer-related mortality over a 5-year follow-up

Objectives: Recent studies have suggested that long-term diuretic therapy may be associated with increased risk of renal cell carcinoma. This carcinoma is not a common malignancy, but it shares risk factors with the considerably more widespread colon cancer (CC). However, there are no data whether or not a relationship between long-term diuretic therapy and CC mortality exists. In this study we tested the hypothesis that long-term diuretic therapy may be associated with increased CC mortality over a 5.6-year follow-up period. Subjects and methods: The study sample comprised 14 166 patients aged 45 to 74 years with a previous myocardial infarction and/or stable anginal syndrome, screened for participation in the bezafibrate infarction prevention (BIP) study. There were 2153 patients receiving diuretics and 12 013 patients receiving no diuretics. Results: During the follow-up 139 (6.5%) new cases of cancer were diagnosed in the diuretic-treated group compared with 622 (5.2%) in the group receiving no diuretics (P = 0.02). Colon cancer mortality was significantly higher in the diuretic-treated patients (0.1 vs 0.5%, P = 0.001), whereas mortality differences for other cancer types were not documented. Multivariate analysis identified diuretics as an independent predictor of increased colon cancer incidence and colon cancer mortality with a hazard ratio (HR) of 2.0 (95% CI 1.2-3.2) for colon cancer incidence and 3.7 (95% CI 1.7-8.3) for mortality. However, the association between diuretic therapy and higher incidence of colon cancer was observed only among non-users of aspirin. A relatively lower colon cancer incidence was observed in the furosemide subgroup, and higher in the small combined amiloride/hydrochlorthiazide subgroup (HR 3.15, 95% CI 1.15-8.65). Conclusion: Long-term exposure to diuretic therapy may be associated with an increased colon cancer-related mortality.