Thrombotic risk in children with acute lymphoblastic leukemia

Thrombotic complications in childhood acute lymphoblastic leukemia: a meta-analysis of 17 prospective studies comprising 1752 pediatric patients

The risk of thrombosis in children with acute lymphoblastic leukemia (ALL) reportedly ranges between 1% and 37%. Epidemiologic studies have usually been hampered by small numbers, making accurate estimates of thrombosis risk in ALL patients very difficult. The aim of this study was to better estimate the frequency of this complication and to define how the disease, its treatment, and the host contribute to its occurrence. We made an attempt to combine and analyze all published data on the association between pediatric ALL and thrombosis, by using a meta-analytic method. The rate of thrombosis in 1752 children from 17 prospective studies was 5.2% (95% CI: 4.2-6.4). The risk varies depending on several factors. Most of the events occurred during the induction phase of therapy. Lower doses of asparaginase (ASP) for long periods were associated with the highest incidence of thrombosis, as were anthracyclines and prednisone (instead of dexamethasone). The presence of central lines and of thrombophilic genetic abnormalities also appeared to be frequently associated with thrombosis. In conclusion, the overall thrombotic risk in ALL children was significant, and the subgroup analysis was able to identify high-risk individuals, a finding that will hopefully guide future prospective studies aimed at decreasing this risk.

Pediatric thrombosis

Although thrombosis is less frequent in children than in adults, it represents a significant source of morbidity and mortality. Multiple factors. both genetic and acquired. contribute to the development of thrombosis in chiidren. Thrombosis in a child warrants investigation of potential underlying prothrombotic conditions. The risk of thrombosis in children with heterozygous deficiencies is not clearly defined, but it appears that children who are heterozygous for more than one risk factor or who have a combination of inherited and acquired defects are at higher risk for thrombosis. Treatment of thrombosis primarily involves a rapidly acting anticoaguiant such as heparin or LMWH to prevent extension, and long-term anticoagulation with warfarin may be instituted to prevent recurrence. Thrombolytic therapy with recombinant tissue plasminogen activator also appears to be safe and effective in children. Prospective and multicenter studies are still needed to clarify the contribution of specific prothrombotic disorders to childhood TE so that evidence-based treatment recommendations can be made.