Comparison of Unfractionated Versus Low Molecular Weight Heparin for Deep Vein Thrombosis Prophylaxis During Breast and Pelvic Cancer Surgery: Efficacy, Safety, and Follow-up

Abstract

In a prospective, double-blind randomized trial the efficacy and safety of low molecular weight heparin and un fractionated heparin were compared for the prevention of post operative deep vein thrombosis in patients undergoing major surgery for breast and pelvic cancer. Three hundred fifty-eight patients were randomly allocated to the two treatment groups. Thirty-four of these were excluded from the study. Of the re maining 324 patients, 164 received 5000 IU unfractionated heparin three times daily and 160 received 3000 anti-Xa units of low molecular weight heparin once daily. Treatment was started 2 to 5 hours preoperatively and continued for 7 days. The occurrence of deep vein thrombosis was determined by impedence plethysmography and/or venography. Deep vein thrombosis was diagnosed in 10 (6.3%) of 160 patients taking low molecular weight heparin and 10 (6.1 %) of 164 patients treated with unfractionated heparin (relative risk: 1.03; 95% confidence interval 0.44-2.39; p = 1.0). Major bleeding events occurred in 27 (16.8%) patients in the low molecular weight heparin group and 47 (28.7%) in the unfractionated heparin group (relative risk: 0.59; 95% confidence interval: 0.39-0.89; p = .01). Severe intraoperative bleeding was observed in three patients in the unfractionated heparin group and in none of the patients in the low molecular weight heparin group. Excessive intraoperative bleeding was less frequent in the low molecular weight heparin group (9.4% vs. 14%, p = .23) as was wound hematoma (11.3 vs. 17.7%, p = .12). Bleeding episodes with low molecular weight heparin were less likely to lead to further surgery for evacuation of hematoma (0.6% vs. 2.5%, p = .37). Perioperative death rate was 3.1 % in the low molecular weight heparin group and 1.8% in unfractionated heparin group (rela tive risk: 1.72, 95% confidence interval: 0.42-7.07; p = .49). Follow-up data were available for 316 patients for an average of 20 months after surgery. There were 35 further cancer deaths (11 low molecular weight heparin group, 24 unfractionated heparin group) and 23 patients with late onset thromboembolic complications (11 low molecular weight heparin group, 12 un fractionated heparin group). The two drugs were of similar efficacy but the frequency of major bleeding was 41.1% less in the low molecular weight heparin group.