WARP - A multicentre prospective randomised controlled trial (RCT) of thrombosis prophylaxis with warfarin in cancer patients with central venous catheters (CVCs)

Abstract

LBA8004 Background: CVC-related thrombosis is a significant cause of morbidity and mortality in cancer patients. Prophylactic practice is varied. We report a large pragmatic RCT of thrombosis prophylaxis in cancer patients receiving chemotherapy via CVCs. The utility of warfarin and 2 dosing strategies was investigated. Methods: Patients, over 16 years old, with solid or haematological malignancies receiving chemotherapy via a CVC, with adequate haematological, hepatic and renal function and no contraindication to, or not currently on warfarin, were randomised according to clinicians’ prescribing practices: Uncertain indication - randomised to control vs warfarin (1mg or dose adjusted warfarin (DAW) to maintain INR between 1.5 and 2.0) Certain indication - randomised to 1mg warfarin vs DAW Patients were stratified by CVC insertion site, chemotherapy regimen and infusion duration. Analysis is on intention-to-treat and the primary endpoint is the number of radiologically proven CVC-related thrombotic events. Thrombosis rates will be compared using a test for proportions. The secondary endpoints of catheter longevity, toxicity and mortality will be investigated using chi-squared and logrank tests. The sample size was calculated to provide 90% power to detect a 10% difference in thrombosis rates between warfarin and no warfarin and 80% power to detect a 7% difference in the warfarin dose comparison (both 2p=0.05). Results: 1590 patients were randomised. In terms of the primary endpoint, patients are followed up for the duration of their CVC and the current median longevity is 105 days (inter-quartile range: 62 to 163). Conclusions: The results of WARP, whether showing benefit for warfarin or not, will impact on clinical practice internationally. No significant financial relationships to disclose.