Thrombosis in children with acute lymphoblastic leukemia: part I. Epidemiology of thrombosis in children with acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. With the advent of aggressive multimodality therapy, ALL has become a curable disease for majority of pediatric patients. Thromboembolism (TE) is a well-recognized serious complication in association with ALL leading to significant morbidity. It can be potentially fatal in over 50% of the affected patients. Development of TE does interfere with the scheduled treatment plan for ALL and, thus, ultimate outcome from ALL. Recent evidence indicates that concomitant administration of asparaginase and steroids is likely to be associated with higher incidence of TE, especially in children with at least one prothrombotic risk factor. In addition, older children and patients with high risk ALL may be at higher risk for developing TE. However, the epidemiology and the exact pathogenesis of this entity have not yet been clearly defined. To reduce the incidence of TE and its impact on overall outcome as well as on the quality of life in children undergoing treatment for ALL, further studies to define the epidemiology of TE in relation to the biology of ALL and chemotherapy protocols are urgently needed. The purpose of this review is to evaluate the current knowledge of TE in association with ALL in children, especially in relation with the treatment protocols and genetic background. This review will be published in three parts. The first part will review the available information regarding epidemiology of TE in children with ALL.