Anticoagulation for the initial treatment of venous thromboembolism in patients with cancer: A systematic review

BACKGROUND. The authors compared the relative efficacy and safety of low-molecular-weight heparin (LMWH) and unfractionated heparin (UFH) for the initial treatment of venous thromboembolism (VTE) between patients with and without cancer. METHODS. By using Cochrane methodology for systematic reviews, separate meta-analyses were conducted for subgroups of patients with and without cancer, and relative risks (RRs) were compared for statistical significance. The methodologic quality for each outcome was assessed by using the Grading of Recommendations Assessment, Development, and Evaluation approach. RESULTS. LMWH reduced mortality significantly compared with UFH in patients with cancer (RR of 0.71; 95% confidence interval [95% CI], 0.52-0.98 [moderate-quality evidence]) but not in patients without cancer (RR of 0.97; 95% CI, 0.65-1.46 [low-quality evidence]). However, the difference in the RR for the 2 subgroups did not reach statistical significance (P = .113). The difference between LMWH and UFH in the effect on recurrent VTE was not statistically significant in the subgroup with cancer (RR of 0.78; 95% CI, 0.29-2.08 [low-quality evidence]), in the subgroup without cancer (RR of 0.94; 95% CI, 0.60-1.46 [low-quality evidence]), or between the 2 subgroups (P = .367). No data were available for bleeding outcomes, thrombocytopenia, or postphlebitic syndrome. CONCLUSIONS. The current results indicated that LMWH most likely is superior to UFH in reducing mortality in the initial treatment of VTE for patients with cancer. There is a need for more and better designed trials to confirm these findings.