Acute lymphoblastic leukemia in infants less than one year of age: a cumulative experience of the Children's Cancer Study Group.

A retrospective review of all 115 infants less than 1 year of age with acute lymphoblastic leukemia (ALL) entered on a consecutive series of recent Children's Cancer Study Group (CCSG) leukemia protocols was undertaken to examine in detail the outcome and clinical course of a large group of similarly treated infants. In comparison to the 4,392 children older than 1 year, entered on the same studies, infants had a significantly (P = .0001) increased incidence of leukocytosis, hepatosplenomegaly, meningeal leukemia at presentation, hypogammaglobulinemia, and failure to achieve complete remission (CR) status by day 14 of induction therapy. In contrast, lymphadenopathy, non-L1 French-American-British (FAB) morphology, mediastinal mass, and T cell leukemia were not more frequently observed. Ninety percent of these infants successfully completed the induction phase of therapy. With a median follow-up of 35 months, life table estimate of disease-free survival is only 23% at 4 years. Identical disease-free survival rates for infants were observed in each of the individual studies reviewed. Excessive toxicity resulting in limitation of therapy delivered was not a causative factor for the disappointing outcome of these patients. Rather, early disease recurrence, characterized by bone marrow relapse (55%) and CNS (22%) relapse, was the major factor responsible for the extremely poor prognosis of this patient group. Identical CNS relapse rates were observed in those patients who received cranial irradiation as part of CNS prophylaxis (21.8%) and in those patients who did not receive cranial radiotherapy (24%). Results of salvage therapy for patients who experienced systemic or extramedullary relapse were dismal. Debilitating neuropsychologic sequellae, presumably related to CNS irradiation, have been observed in 50% of the small number of long-term survivors. Infants less than 1 year of age with ALL present with a constellation of features which predict a poor outcome and constitute the group of children with ALL at greatest risk for treatment failure.