Maintenance chemotherapy for childhood acute lymphoblastic leukaemia: better in the evening.

The course of 118 children with acute lymphoblastic leukaemia who had achieved complete remission with a standard induction protocol and had also received meningeal prophylaxis with intrathecal methotrexate (MTX) and cranial irradiation was reviewed. Maintenance chemotherapy consisted of daily 6-mercaptopurine (6-MP), weekly MTX, and monthly vincristine and prednisone. 82 children took 6-MP and MTX in the morning and 36 in the evening. Disease-free survival as determined by Kaplan-Meier analysis was better for children on evening chemotherapy. Regression analysis (Cox proportional hazards model, with evening vs morning schedule as exposure variable, and age at diagnosis, leucocytosis at diagnosis, and sex as covariates) showed that, for those surviving free of disease for longer than 78 weeks, the risk of relapsing was 4.6 times greater for the morning schedule than for the evening one.