Efficacy of high-dose methotrexate in childhood acute lymphocytic leukemia: analysis by contemporary risk classifications. 
High-dose methotrexate (HDMTX) added to a basic regimen of chemotherapy proved superior to cranial irradiation and sequentially administered drug pairs (RTSC) in prolonging complete remissions in children with "standard-risk" acute lymphocytic leukemia.  To extend this result to more contemporary risk groups, we reclassified the patients according to methods of the Pediatric Oncology Group (POG), the Childrens Cancer Study Group (CCG), the Rome workshop, and St Jude Total Therapy Study XI.  By life table analysis, 70% to 78% of patients with a favorable prognosis would remain in continuous complete remission (CCR) at 4 years if treated with HDMTX.  Uniformly lower CCR rates could be expected with RTSC, especially in St Jude better-risk patients.  HDMTX also would show greater efficacy than RTSC in the CCG average-risk and POG poor-risk groups, but the results appear inferior to those being achieved with intensified regimens for high-risk leukemia.  Although both therapies would provide adequate CNS prophylaxis in favorable-risk groups, RTSC would offer greater protection in patients classified as being in a worse-risk group by St Jude criteria.  We conclude that HDMTX-based therapy, as described in this report, would be most effective in patients with a presenting leukocyte count of less than 25 x 10(9)/L, of the white race, aged 2 to 10 years, and having leukemic cell hyperdiploidy without translocations.