Does warfarin therapy influence the risk of bladder cancer?

There has been growing interest in studying the biological effects of certain drugs and their potential to reduce the risk of various cancers. One study reported a decrease in the incidence of urogenital cancers in a trial with patients who received warfarin for treatment of venous thromboembolism, but a limitation to this study of urogenital cancers was the very small number of bladder cancer cases that developed following warfarin therapy. The objective of the present study is to measure the association between warfarin use and bladder cancer. A total of 330 cases with bladder cancer were identified at the James A. Haley Veterans' Administration (VA) Hospital in Tampa, Florida, using a combination of computerized pathology records and inpatient and outpatient diagnoses. Controls were randomly selected from the VA computerized administrative database and 1293 controls were included for analysis. Unconditional logistic regression analysis was performed to assess the risk of bladder cancer after adjusting for age, gender, and cigarette smoking. Among warfarin users, although there was a 27% elevation in risk, it did not differ significantly from nonusers (OR = 1.27, 95% CI = 0.85, 1.89). No duration-response relationship was observed between anticoagulant use and risk of bladder cancer. The results suggest that warfarin does not protect against bladder cancer, at least in male smokers, the highest risk population for bladder cancer.