Low-molecular-weight-heparin versus a coumarin for the prevention of recurrent venous thromboembolism in high- and low-risk patients with active cancer: a post hoc analysis of the CLOT Study

In patients with active cancer and acute venous thromboembolism (VTE), the low-molecular-weight-heparin (LMWH) dalteparin is more effective than vitamin K antagonist (VKA) in reducing the risk of recurrent venous thromboembolism (rVTE) without increasing the risk of bleeding. However, the relative benefit of LMWH versus VKA in patients with active cancer at high or low risk of rVTE and bleeding is unclear. This post hoc analysis used data from the CLOT study to explore the efficacy and safety of LMWH versus VKA in preventing recurrent thrombosis in high- and low-risk patients with active cancer. High-risk patients were defined by metastatic disease and/or antineoplastic treatment at baseline; low-risk patients presented with neither. Among high-risk patients, rVTE occurred in 25/318 (8%) (LMWH) versus 53/314 (17%) (VKA) (hazard ratio, 0.44; p = 0.001). No significant difference was detected in the rate of major or any bleeding. The 6-month mortality rate was 40% (LMWH) versus 41% (VKA). In low-risk patients, 2/20 (10%) (LMWH) had rVTE versus 0/24 (0%) (VKA) (hazard ratio, not estimable; p = 0.998). No significant difference was detected in the rate of major or any bleeding. The 6-month mortality rate was 20% (LMWH) versus 29% (VKA). In patients with cancer-associated thrombosis at high risk of rVTE and bleeding, the LMWH dalteparin was more effective than VKA in reducing the risk of rVTE without increasing the risk of bleeding. No difference in rate of rVTE or bleeding was observed between LMWH and VKA among low-risk patients.