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Treating childhood leukemia without cranial irradiation.

To the Editor: Pui and colleagues (June 25 issue)1 report a high likelihood of event-free and overall survival among children with acute lymphoblastic leukemia (ALL) treated with an intensive regimen of intrathecal chemotherapy and systemic drugs that penetrate the central nervous system (CNS). Their goal was to eliminate cranial irradiation and its late toxic effects. Most other trials of treatment for childhood ALL already treat the majority of patients (80% or more) without cranial irradiation, with similarly favorable results. Indeed, only 14% of patients in the study reported on by Pui et al. would have received cranial irradiation in previous trials. In these patients, survival did not appear to be adversely affected by the elimination of irradiation. Although the overall outcome of this trial was favorable, some subgroups of patients remained at high risk for relapse. Also, the acute systemic and CNS toxic effects of the treatment were not insubstantial, and the long-term neurocognitive outcomes are unknown. Before this investigational approach can be considered the standard of care, its consequences should be more thoroughly evaluated, ideally in randomized trials with larger numbers of patients and longer follow-up. Stephen E. Sallan, M.D.