Warfarin is safe as secondary prophylaxis in patients with cancer and a previous episode of venous thrombosis

The purpose of this study was to establish the safety and efficacy of sodiu m warfarin in the secondary prophylaxis of venous thrombosis in patients wi th cancer. This was an inception cohort study of patients enrolled in an an ticoagulation clinic between July 1991 and October 1996. The rates of bleed ing and recurrent thrombosis were evaluated in all the patients, and the re sults in patients with cancer (n = 104) were compared with those without ca ncer (n = 208). The rate of major hemorrhage was 0.4% and 0.3% per treatmen t month in the patients with cancer and those without cancer, respectively. The rates of recurrent thrombosis were 1.2% and 0.2% per treatment month i n the patients with cancer compared with those without cancer, respectively . We conclude that warfarin is safe when used for the secondary prophylaxis of patients with cancer who have had a venous or arterial thrombosis, and the risk of major hemorrhage is not significantly different when compared w ith the risk in patients without cancer. The rate of recurrent thrombosis i s approximately sixfold higher in patients with cancer being treated with w arfarin for secondary prophylaxis of thrombosis compared with patients with out cancer. Nonetheless, the rate of recurrent thrombosis is not overly exc essive, and warfarin can be viewed as a relatively effective form of therap y for these patients.