Background: As a first step to formulate a new treatment strategy for refractory acute lymphoblastic leukemia (ALL) in infants, clinical results and immunophenotypic and cytogenetic data were analyzed and compared with those from overseas.
Methods: There were 62 infants with ALL who were treated between 1977 and 1995 at 30 institutions affiliated with the Tokyo Children's Cancer Study Group. Clinical and laboratory data obtained from these infants (all under 1 year of age) were retrospectively studied.
Results: The morphological diagnoses were FAB-L1 for 51 patients (82.2%) and FAB-L2 for 11 patients (17.8%). Hepatomegaly and splenomegaly were found in 40 (70.0%) and 40 patients (68.3%), respectively. The mean (+/- SEM) leukocyte count at diagnosis was 205,900 +/- 35,700/microL. The involvement of the central nervous system was evident in nine of 36 patients who were subjected to lumbar puncture, while three of these nine patients were free of neurological symptoms at diagnosis. Thirty-one patients (55.4%) were CD10 negative and 14 (25.0%) were CD10 positive. Thirty-one of 47 patients (65.9%) exhibited chromosomal abnormalities, including 28 patients (59.6%) with 11q23 abnormalities. Rearrangements in the MLL gene were found in nine of 13 infants (69.2%) examined. Translocation of 11q23 and/or MLL gene rearrangement (11q23/MLL) was significantly associated with the absence of the CD10 antigen. Hyperleukocytosis of more than 50,000/microL and 11q23/MLL gene rearrangements were related to a poor prognosis. The probability of an event-free survival in 62 infants was 13.1 +/- 4.8% at 48 months.
Conclusions: New therapeutic strategies and large-scale cooperative prospective trials are needed to improve the prognosis of ALL in infants.