Is recurrent venous thromboembolism after therapy reduced by low-molecular-weight heparin compared with oral anticoagulants?

Purposes: To evaluate whether the incidence of recurrent venous thromboembolism (VTE) events after therapy differs for patients treated with long-term low-molecular-weight heparin (LMWH) or oral anticoagulant therapy (OAT).

Methods: All randomized studies were searched through computerized queries of MEDLINE, the Cochrane Controlled Trials Register, the American Society of Hematology abstract database, and the American Society of Clinical Oncology abstract database.

Results: Eleven studies including 2,907 patients were identified. Seven studies evaluated a period of 3 to 9 months after cessation of the allocated treatment: 5.4% of patients in the LMWH group vs 4% in the arm allocated to OAT had an episode of recurrent symptomatic VTE. Combined analysis showed a nonsignificant trend in lowering recurrent symptomatic VTE in favor of OAT (relative risk [RR], 1.29; 95% confidence interval [CI], 0.82 to 2.02; p = 0.27). By contrast, during active treatment, a statistically significant reduction of the risk of recurrent symptomatic VTE in favor of LMWH over OAT was registered (RR, 0.63; 95% CI, 0.47 to 0.83; p = 0.001). Regarding cancer patients only, 37 of 569 patients (6.5%) in the LMWH group had recurrent symptomatic VTE vs 69 of 546 patients (12.6%) in the OAT group, with a statistically significant reduction of the risk of recurrent symptomatic VTE in favor of LMWH (RR, 0.52; 95% CI, 0.35 to 0.76; p = 0.001).

Conclusions: Despite the significant reduction of the risk of recurrent symptomatic VTE in favor of LMWH over OAT during treatment, patients treated with long-term LMWH do not seem to have more frequently recurrent VTE events compared with OAT after cessation of therapy. The significant difference favoring LMWH over OAT among all patients receiving treatment comes mostly from studies enrolling cancer patients.