Anticoagulation for the initial treatment of venous thromboembolism in patients with cancer
Abstract
Background
Compared to patients without cancer, patients with cancer who receive anticoagulant treatment for venous thromboembolism are more likely to develop recurrent venous thromboembolism (VTE).
Objectives
To compare the efficacy and safety of three types of parenteral anticoagulants for the initial treatment of VTE in patients with cancer.
Search methods
A comprehensive search for studies of anticoagulation in cancer patients including a February 2010 electronic search of: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and ISI Web of Science.
Selection criteria
Randomized clinical trials (RCTs) comparing low molecular weight heparin (LMWH), unfractionated heparin (UFH), and fondaparinux in patients with cancer and objectively confirmed VTE.
Data collection and analysis
Using a standardized data form, data was extracted in duplicate on methodological quality, participants, interventions, and outcomes of interest that included mortality, recurrent VTE, major bleeding, minor bleeding, postphlebitic syndrome, quality of life, and thrombocytopenia.
Main results
Of 3986 identified citations, 16 RCTs were eligible: 13 compared LMWH to UFH, two compared fondaparinux to heparin, and one compared dalteparin to tinzaparin. Meta‐analysis of 11 studies showed a statistically significant reduction in mortality at three months of follow up with LMWH compared with UFH (relative risk (RR) 0.71; 95% confidence interval (CI) 0.52 to 0.98). There was little change in the effect estimate after excluding studies of lower methodological quality (RR 0.72; 95% CI 0.52 to 1.00). A meta‐analysis of three studies comparing LMWH with UFH showed no statistically significant reduction in VTE recurrence (RR 0.78; 95% CI 0.29 to 2.08). The overall quality of evidence was low for LMWH versus UFH due to imprecision and likely publication bias. There were no statistically significant differences between heparin and fondaparinux for the outcomes of death (RR 1.27; 95% CI 0.88 to 1.84), recurrent VTE (RR 0.95; 95% CI 0.57 to 1.60), major bleeding (RR 0.79; 95% CI 0.39 to1.63) or minor bleeding (RR 1.50; 95% CI 0.87 to 2.59). The one study comparing dalteparin to tinzaparin did not find a statistically significant difference in mortality (RR 0.86; 95% CI 0.43 to 1.73).
Authors' conclusions
LMWH is possibly superior to UFH in the initial treatment of VTE in patients with cancer. Additional trials focusing on patient important outcomes will further inform the questions addressed in this review.
PICOs
Plain language summary
Blood thinners for the initial treatment of blood clots in patients with cancer
Patients with cancer are at an increased risk of blood clots. The blood thinner administered in the first few days can consist of unfractionated heparin (infused intravenously) or low molecular weight heparin (injected subcutaneously once or twice per day). These two blood thinners may have different efficacies and safety profiles. In this systematic review, data from 13 studies suggest that low molecular weight heparin is superior to unfractionated heparin in reducing mortality. However, there is not enough evidence to prove superiority in reducing recurrence of blood clots. We did not find data to compare the safety profile of these two medications.
