BERKELEY, CA (UroToday Inc.) - Without question, patients with cancer at a higher risk for thromboembolic events. Until very recently, the decision to place a patient with deep vein thrombosis (DVT) on coumarin or low molecular weight heparin was largely based on drug cost or patient convenience. A landmark study (CLOT study) published in the New England Journal of Medicine (N Engl J Med. 2003 Jul 10;349(2):146-53), however, showed that dalteparin was more effective in preventing DVT than coumarin derivatives without increasing bleeding risk.

Recent experimental studies and indirect clinical evidence suggest that low molecular weight heparins may possess antineoplastic effects. In particular, laboratory data show that these drugs may exert their antitumor effect via a dose-dependent antiangiogenic mechanism. In the CLOT study, however, no difference was seen in survival between dalteparin and coumarin derivatives, potentially because patients with metastatic disease were grouped together with patients without disseminated disease.

In the April 1st issue of the Journal of Clinical Oncology, Lee and colleagues from within the CLOT study report on a cohort of 602 patients with solid tumors and DVT who were randomly assigned to dalteparin or a coumarin derivative for 6 months. The main objective of the study was to compare all-cause mortality after 12 months between treatment groups in patients with and without metastatic malignancy

Overall mortality after 12 months for all patients with DVT and solid tumors was 59%. Among patients without metastastic disease, the probability of death at 1 year was 20% in the dalteparin group compared with 36% in the coumarin group (hazard ratio, 0.50; 95% CI, 0.27 to 0.95; P = .03). There was no difference between groups in patients with metastastic disease.

In patients with a DVT and a solid tumor without metastatic disease, the use of low-molecular weight heparin was associated with a 44% reduction in all-cause death compared with patients randomized to receive a coumarin derivative. Laboratory evidence suggesting an antiangiogenic effect of low-molecular weight heparin is currently under intense study.

J Clin Oncol 23:2123-2129