Prophylactic Cranial Irradiation for Acute Lymphoblastic Leukemia in Childhood

Shinn, Kyung Sub; Kang, Ki Mun; Kim, Hack Ki; Choi, Ihl Bhong; Kim, In Ah

Abstract

PURPOSE: This report is the result of retrospective analysis for children who received prophyactic cranial irradiation combined with intrathecal chemotherapy.
METHODS
AND MATERIALS: Ninety children with ALL who had got bone marrow remission after induction chemotherapy received PCI. All but 3 children were treated with a dose of 1800 cGy as a standard regimen. While the PCI was given, all patients received intrathecal chemotherapy.
RESULTS
Nine of 90 patients experienced CNS relapse during the duration of follow-up ranged from 36 to 96 months (median 60 months). Three children experienced BM relapse prior to CNS relapse. Therefore, CNS relapse rate as the first adverse event was 6.7%. Median time interval of CNS relapse was 16 months from the first day of hematologic complete remission. Eighty-nine percent of patients who had CNS relapse occurred during maintenance chemotherapy (on-therapy relapse). The CNS RFS at 2 and 5 years are 68 % and 42 %, respectively with median of 43 months. The prognostic factors affecting CNS RFS are initial WBC count (cut-off point of 50,000/mul), FAB subtype and CALGB risk WBC count (cut-off point of 50,000/mul), FAB subtype, POG and CALGB risk criteria.
CONCLUSION
In our study, 6.7% of CNS relapse rate as a first adverse event was comparable with other studies. Various risk criteria was based on age at diagnosis and initial WBC count such as POG and CALGB criteria, had prognostic significance for CNS RFS and DFS. Prospective randomized trial according to prognostic subgroup based on risk criteria and systematic study about neuropsychologic function for long term survivors, are essential to determine the most effective and least toxic form of CNS prophylaxis.