CATCH: a randomised clinical trial comparing long-term tinzaparin versus warfarin for treatment of acute venous thromboembolism in cancer patients

Background: Low-molecular-weight heparin (LMWH) is recommended and commonly used for extended treatment of cancer-associated thrombosis (CAT), but its superiority over warfarin has been demonstrated in only one randomised study. We report here the rationale, design and a priori analysis plans of Comparison of Acute Treatments in Cancer Haemostasis (CATCH; NCT01130025), a multinational, Phase III, open-label, randomised controlled trial comparing tinzaparin with warfarin for extended treatment of CAT. Methods/Design: The primary objective is to assess the efficacy of tinzaparin in preventing recurrent venous thromboembolism (VTE) in patients with active cancer and acute, symptomatic proximal deep vein thrombosis and/or pulmonary embolism. The secondary objectives are to determine: safety of tinzaparin given over 6 months; clinical and laboratory markers for recurrent VTE and/or major bleeding; 6-month overall mortality; incidence and severity of post-thrombotic syndrome; patient-reported quality of life; and healthcare resource utilisation. Nine hundred patients are randomised to receive tinzaparin 175 IU/kg once daily for 6 months or initial tinzaparin 175 IU/kg once daily for 5-10 days and dose-adjusted warfarin (target INR 2.0-3.0) for 6 months. The primary composite outcome is time to recurrent VTE, including incidental VTE and fatal pulmonary embolism. All patients are followed up to 6 months or death, whichever comes sooner. Blinded adjudication will be performed for all reported VTE, bleeding events and causes of death. Efficacy will be analysed using centrally adjudicated results of all patients according to intention-to-treat analysis. An independent Data Safety Monitoring Board is reviewing data at regular intervals and an interim analysis is planned after 450 patients have completed the study. Discussion: The results will add significantly to the knowledge of the efficacy, safety and cost effectiveness of tinzaparin in the prevention of recurrent VTE in patients with cancer and thrombosis. Prospective data will emerge on the clinical significance of incidental VTE and risk stratification in patients with CAT. Results on post-thrombotic syndrome, quality of life and healthcare resource utilisation will inform decision makers on how to secure better patient care. If tinzaparin is shown to be more effective than warfarin, CATCH will provide valuable confirmatory data to support the use of the LMWH tinzaparin for extended treatment of CAT.