Treatment of deep venous thrombosis with low molecular weight heparin in pediatric cancer patients: safety and efficacy.

Few complete reports exist regarding treatment of venous thromboembolism in children undergoing chemotherapy. We designed this study to unify the treatment of venous thromboembolism in oncology pediatric patients at our department. At the same time, we wanted to evaluate the safety and efficacy of our newly designed treatment schedule. Data from pediatric oncology patients with deep venous thrombosis (DVT) treated at the Department of Pediatric Oncology, Brno, was collected prospectively over a 2-year period (1 January 2006 to 31 December 2007). All patients received low molecular weight heparin (LMWH) at an initial dose of 1.2-1.5 mg/kg body weight subcutaneously (s.c.) twice daily for the first 7-10 days. Afterwards, the dose was lowered to 1.5 mg/kg s.c. once daily. We kept this dose unchanged for a minimum of 3 months. For the first 6 weeks of treatment, the platelet count was maintained 20 x 10/l or more with no concomitant LMWH withdrawal. For the rest of the treatment, LMWH was interrupted once platelets dropped below 20 x 10/l. A total of 33 patients were followed for a median of 6 months. DVT was symptomatic in 15 of 33 patients (46%) and asymptomatic in 18 of 33 (54%) patients. Complete thrombus resolution occurred in 22 of 33 (67%) patients, partial or no recanalization was achieved in 11 of 33 (33%) patients. Eight patients (eight of 33, 24%) were diagnosed with postthrombotic syndrome (PTS). The risk of PTS was significantly higher for patients with symptomatic DVT than in those with asymptomatic DVT. Neither patency rates nor the risk of PTS showed a positive correlation with the achievement of therapeutic anti-Xa activity. Thrombocytopenia less than 20 x 10/l occurred at least once during LMWH treatment in 30/33 (91%) patients. None of the patients experienced severe bleeding, whereas mild bleeding episodes were observed in five of 33 (15%) patients. Our treatment schedule has proved to be both well tolerated and reasonably efficient in treating DVT in children undergoing chemotherapy. Further studies on larger patient groups are warranted.