Low numbers of CSF blasts at diagnosis do not predict for the development of CNS leukemia in children with intermediate-risk acute lymphoblastic leukemia: A Childrens Cancer Group report

Purpose: This study was designed to evaluate the effect on CNS relapse (CNSR) and overall relapse rates of blast cells in the CSF containing ≤ 5 cells/μL at the time of diagnosis of intermediate-risk acute lymphoblastic leukemia (ALL) in children entered onto a large randomized multicenter prospective therapeutic trial (Childrens Cancer Group [CCG]-105). Patients and Methods: We studied outcome in terms of CNSR and event-free survival (EFS) in 1,544 patients who successfully completed remission-induction therapy and had been randomized to one of four systemic chemotherapy regimens and to one of two CNS prophylaxis regimens. We compared outcome between 1,450 patients who had varying degrees of pleocytosis but no blasts in the CSF at diagnosis (blast-negative group) with 94 who had blasts detected in the CSF after cytocentrifugation but had a total CSF WBC count of ≤ 5/μL (blast- positive group). Results: No statistically significant differences in overall CNSR or EFS rates were observed between the two groups and no differences were found when analyzed according to age or WBC count at diagnosis, sex, or type of CNS prophylaxis (intrathecal [IT] methotrexate [MTX] alone v IT MTX plus 18 Gy cranial irradiation [CXRT]). Conclusion: In intermediate-risk ALL, there was no significant difference in CNSR and systemic relapse rates after standard presymptomatic CNS therapy between patients with a CSF WBC count ≤ 5/μL and those without identifiable blasts in the CSF. These findings suggest that certain approaches to therapy, such as that used in this study, may eliminate the need for any additional special treatment directed at this subset of patients with CSF blasts.