Clinical Question

For patients with cancer and venous thromboembolism (VTE), is low-molecular-weight heparin (LMWH) or an oral anticoagulant (vitamin K antagonists warfarin [Coumadin] or acecumarol [not available in the United States]) more effective for preventing recurrent VTE?

Evidence-Based Answer

Although LMWH appears to be more effective than oral anticoagulants in the prevention of recurrent VTE, this does not translate into a survival benefit. LMWH and oral anticoagulants have the same reported adverse events of bleeding and thrombocytopenia.

Practice Pointers

Patients with cancer have a higher incidence of recurrent VTE (deep venous thrombosis and pulmonary embolism) compared with patients without cancer (27.1 versus 9.0 events per 100 patient-years; P = .003) and a higher risk of major bleeding when anticoagulated (13.3 versus 2.2 events per 100 patient-years; P = .002). Although there are many studies comparing LMWH and warfarin for prevention of recurrent VTE, this is the first systematic review to address the effectiveness and safety of anticoagulation in the subset of patients with cancer.

The authors of this Cochrane review identified eight randomized controlled trials studying the effectiveness and safety of LMWH compared with oral anticoagulants in patients with cancer and VTE who were older than 18 years. Outcomes were measured at three, six, and 12 months.

Pooled analyses showed no statistically significant survival benefit of LMWH over oral anticoagulants or in all-cause mortality at three or six months. Pooled analysis of three studies (n = 1,109) showed a statistically significant benefit of LMWH over oral anticoagulants for recurrent VTE outcome (hazard ratio = 0.47; 95% confidence interval, 0.32 to 0.71). These three studies reported recurrent VTE at three, six, or 12 months. In terms of harms, there were no differences between the LMWH and oral anticoagulant groups in the reported incidence of minor or major bleeding or thrombocytopenia, based on a meta-analysis of four studies.

The American Academy of Family Physicians and American College of Physicians joint clinical practice guideline recommends LMWH or oral anticoagulation in the long-term treatment of VTE and suggests that LMWH may be more effective in patients with cancer.¹ The American Society of Clinical Oncology (ASCO) recommends that all patients with cancer who also have established VTE should be treated with LMWH for at least six months; warfarin (International Normalized Ratio goal 2 to 3) is an acceptable alternative if LMWH is not available. Based on consensus opinion, ASCO recommends indefinite anticoagulation (with LMWH, if available) for patients with metastatic cancer or those receiving ongoing chemotherapy.²