Randomized placebo-controlled study of low-dose warfarin for the prevention of central venous catheter-associated thrombosis in patients with cancer

Purpose In this multicenter, randomized, placebo-controlled clinical trial, we studied whether warfarin 1 mg daily reduces the incidence of symptomatic central venous catheter (CVC)-associated thrombosis in patients with cancer. Patients and Methods Two hundred fifty-five patients with cancer who required a CVC for at least 7 days were randomly assigned to receive warfarin 1 mg or placebo. Results There were 11 (4.3 %) symptomatic CVC-associated thromboses among 255 patients, with no difference in the incidence of symptomatic CVC-associated thrombosis between patients taking warfarin 1 mg daily (six of 130 patients; 4.6 %) and patients taking placebo (five of 125 patients; 4.0 %; hazard ratio, 1.20; 95 % Cl, 0.37 to 3.94). Warfarin had no effect on CVC life span (84 days v 63 days in control and warfarin groups, respectively; 95 % confidence limit, -16 to 55 days; P = .09), and it did not affect the number of premature CVC removals (23.2 % v 25.4 % in control and warfarin groups, respectively; 95 % confidence limit of difference -8.34 to 12.71; P = .68) or the frequency of major bleeding episodes (2 % v 0 % in control and warfarin groups, respectively; P = .5, Fisher's exact test). Conclusion Symptomatic CVC-associated thrombosis in patients with cancer, although significant, is less common than previously reported. In this study, the administration of warfarin 1 mg daily did not reduce the incidence of symptomatic CVC-associated thrombosis in patients with cancer. However, the low rate of symptomatic CVC-associated thrombosis means that a much larger trial is required to address this issue definitively.