Recent advances in the biology and treatment of childhood acute lymphoblastic leukemia.

As cure rates in childhood acute lymphoblastic leukemia edge toward 80%, the focus of research is shifting to better means of identifying and treating resistant cases. This new emphasis has stimulated progress in several areas. Recent findings suggest that poor early responses to therapy and detection of minimal residual disease at the postremission induction period by immunologic methods are reliable indicators of an adverse prognosis warranting modification of treatment. In this regard, timely administration of intensified chemotherapy, including a second reinduction/intensification phase, may nullify the adverse prognosis conferred by a delayed response to induction therapy. Comparative analysis of survival outcomes in T-cell patients who received chemotherapy or cranial irradiation (12 Gy) to prevent overt leukemia in the central nervous system suggests that the latter modality should be retained for cases with leukocyte counts > 100 x 10(9)/L. Recent innovations in histocompatibility matching, prevention of graft-versus-host disease, and antiviral prophylaxis have enhanced the applicability of hematopoietic stem cell transplantation, making this procedure available to candidates lacking matched sibling donors. Finally, demonstration that acute lymphoblastic leukemia has an angiogenic phase in bone marrow raises the possibility of effective treatment with antiangiogenic agents, such as endostatin. Remaining challenges in the treatment of childhood leukemia include 1) the development of specific and more effective therapy for high-risk cases and 2) the reduction of long-term complications associated with intensive chemotherapy and cranial irradiation.