
Thromboembolism affects many patients with solid tumors and clonalhematologic malignancies. Thromboprophylaxis with low-molecularweightheparin (LMWH) is indicated for surgery and other high-risksituations, but not routinely for central venous catheters or nonsurgical,ambulatory management. Thrombotic events require full anticoagulationfor the duration of active disease and/or the prothromboticstimulus. LMWHs are safe and more effective than both unfractionatedheparin for initial therapy and warfarin for secondary prevention. Antiinflammatoryand antiangiogenic properties might account for thisadvantage and for a survival benefit of chronic LMWH in subgroupsof cancer patients. Ongoing studies are characterizing the cost-effectivenessand antitumor mechanisms of LMWHs, the potential utility ofnewer anticoagulants, and the ability of predictive models to identifyhigh-risk candidates for thromboprophylaxis.

