Comparison of low-molecular-weight heparin and antithrombin versus antithrombin alone for the prevention of symptomatic venous thromboembolism in children with acute lymphoblastic leukemia

Background. Children with acute lymphoblastic leukemia (ALL) have a substantial risk for thromboembolism (TE) that is related to L-asparaginase-induced antithrombin (AT) deficiency and placement of central venous lines. Recent in vitro studies showed that the anticoagulant effects of low-molecular-weight heparin were profoundly affected by endogenous AT levels in children undergoing ALL therapy. Methods. A total of 112 consecutively recruited children with newly diagnosed ALL treated according to BFM 95/ 2000 protocols were enrolled in this trial. This prospective cohort study was carried out to determine the influence of combined low molecular weight heparin-prophylaxis (enoxaparin 1 mg/kg/per day) and AT supplementation versus AT alone (noncontemporaneous control group) on the incidence of symptomatic TE during a follow-up of 240 days. Results. To maintain AT plasma levels above 50%, nearly 60% of all children needed at least one, most children two or three AT supplementations during induction therapy. 12.7% of the children that did receive only AT-prophylaxis (n=71) (95% CI=6.0-22.7) developed objectively confirmed symptomatic TE, as compared with no TE in children after combined prophylaxis (n=41) (95% CI=0.0-8.6, P<0.05). Thromboses were located in the sinovenous system in the brain (n=3), the lower deep veins (n=3), the upper deep veins (n=2) and in an upper deep vein combined with pulmonary embolism (n=1). Conclusion. Prophylaxis with enoxaparin was safe and effective in preventing TE. Although our data are encouraging, the in vivo efficacy of combined enoxaparin and AT prophylaxis to prevent symptomatic venous TE in children with ALL should be evaluated in a prospective randomized clinical trial.