Blasts in CSF with a normal cell count do not justify alteration of therapy for acute lymphoblastic leukemia in remission: A Childrens Cancer Group study

Purpose: The Childrens Cancer Group (CCG) requires both a CSF WBC count of more than five cells per microliter and demonstration of blast cells in the cytocentrifuge specimen to support a diagnosis of CNS relapse. We reviewed the CSF examinations of patients with intermediate-risk acute lymphoblastic leukemia (ALL) to determine the clinical significance of blast cells reported in the cytocentrifuge when the total CSF cell count was normal. Patients and Methods: Children treated on CCG-105 for ALL had CSF examinations every 12 weeks during maintenance therapy. The outcome of children who had a positive CSF cytocentrifuge examination without an elevated CSF WBC count was compared with that of children who did not have any CSF blast cells observed. Results: Sixty-four patients had 81 CSF examinations with blast cells and a normal cell count. By Cox life-table regression analysis, patients with blasts had a different disease-free survival (DFS) distribution, with relapses tending to occur earlier (P = .008). However, the DFS for these patients was 63% ± 9.6% at 5 years from the time of the abnormal cytocentrifuge result as compared with 69% ± 1.5% for 1,490 children who did not have blasts in their CSF. This difference is not significant. Conclusion: Blast cells were infrequently identified in cytocentrifuge preparations of CSF when the cell count was normal. The majority of patients in whom such an event was observed have not experienced a subsequent relapse as measured by life-table analysis at 5 years. The data do not justify changing or augmenting therapy based on cytocentrifuge results alone.