{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T00:42:39Z","timestamp":1790901759342,"version":"4.1.0"},"reference-count":31,"publisher":"American Society of Clinical Oncology (ASCO)","issue":"7","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JCO"],"published-print":{"date-parts":[[2000,4,7]]},"abstract":"<jats:p> PURPOSE: We postulated that intensification of chemotherapy immediately after remission induction might reduce the leukemic cell burden sufficiently to allow an abbreviated period of antimetabolite therapy. <\/jats:p><jats:p> PATIENTS AND METHODS: Three hundred forty-seven children (ages 1 to 15 years) with previously untreated acute lymphoblastic leukemia (ALL) were enrolled onto the Tokyo L92\u201313 study, which excluded patients with mature B-cell ALL and patients less than 1 year old. One hundred twenty-four patients were classified as standard risk, 122 as high risk, and 101 as extremely high risk, according to age, peripheral-blood leukocyte count, selected genetic abnormalities, and immunophenotype. All subjects received four drugs for remission induction, followed by a risk-directed multidrug intensification phase and therapy for presymptomatic leukemia in the CNS. Maintenance chemotherapy with oral mercaptopurine and methotrexate was administered for 6 months, with all treatment stopped by 1 year after diagnosis. <\/jats:p><jats:p> RESULTS: The mean (\u00b1 SD) event-free survival (EFS) and overall survival rates for all patients were 59.5% \u00b1 3.4% and 81.5% \u00b1 2.2%, respectively, at 5.5 years after diagnosis. EFS rates by risk category were similar (60.2% \u00b1 6.0% for standard risk, 57.7% \u00b1 5.6% for high risk, and 62.5% \u00b1 5.7% for extremely high risk), whereas overall survival rates differed significantly (91.2% \u00b1 2.7%, 80.0% \u00b1 4.1%, and 72.1% \u00b1 4.5%, respectively, P &lt; .0001 by the log-rank test). There were 107 relapses. Eighty-five (79.4%) of these 107 patients achieved second complete remissions, with subsequent EFS rates of 61.5% \u00b1 7.9% (standard risk), 42.6% \u00b1 8.1% (high risk), and 9.6% \u00b1 6.4% (extremely high risk). Of the five risk factors analyzed, only the response to prednisolone monotherapy among extremely high-risk patients proved important. <\/jats:p><jats:p> CONCLUSION: Early treatment intensification did not compensate for a truncated phase of maintenance chemotherapy in children with standard- or high-risk ALL. However, 6 months of antimetabolite treatment seemed adequate for extremely high-risk patients who were good responders to prednisolone and received intensified chemotherapy that included high-dose cytarabine early in the clinical course. <\/jats:p>","DOI":"10.1200\/jco.2000.18.7.1508","type":"journal-article","created":{"date-parts":[[2017,2,24]],"date-time":"2017-02-24T02:12:37Z","timestamp":1487902357000},"page":"1508-1516","source":"Crossref","is-referenced-by-count":90,"title":["Six Months of Maintenance Chemotherapy After Intensified Treatment for Acute Lymphoblastic Leukemia of Childhood"],"prefix":"10.1200","volume":"18","author":[{"given":"Yasunori","family":"Toyoda","sequence":"first","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; Department of Pediatric Hematology\/Oncology, The University of Tokyo, The Institute of Medical Science; The First Department of Pediatrics, Toho University School of Medicine; Departments of Pediatrics at Tokyo Medical and Dental University School of Medicine, Keio University School of Medicine, Juntendo University School of Medicine, Nippon Medical..."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Atsushi","family":"Manabe","sequence":"additional","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; Department of Pediatric Hematology\/Oncology, The University of Tokyo, The Institute of Medical Science; The First Department of Pediatrics, Toho University School of Medicine; Departments of Pediatrics at Tokyo Medical and Dental University School of Medicine, Keio University School of Medicine, Juntendo University School of Medicine, Nippon Medical..."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masahiro","family":"Tsuchida","sequence":"additional","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; Department of Pediatric Hematology\/Oncology, The University of Tokyo, The Institute of Medical Science; The First Department of Pediatrics, Toho University School of Medicine; Departments of Pediatrics at Tokyo Medical and Dental University School of Medicine, Keio University School of Medicine, Juntendo University School of Medicine, Nippon Medical..."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ryohji","family":"Hanada","sequence":"additional","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; Department of Pediatric Hematology\/Oncology, The University of Tokyo, The Institute of Medical Science; The First Department of Pediatrics, Toho University School of Medicine; Departments of Pediatrics at Tokyo Medical and Dental University School of Medicine, Keio University School of Medicine, Juntendo University School of Medicine, Nippon Medical..."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Koichiro","family":"Ikuta","sequence":"additional","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; Department of Pediatric Hematology\/Oncology, The University of Tokyo, The Institute of Medical Science; The First Department of Pediatrics, Toho University School of Medicine; Departments of Pediatrics at Tokyo Medical and Dental University School of Medicine, Keio University School of Medicine, Juntendo University School of Medicine, Nippon Medical..."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuri","family":"Okimoto","sequence":"additional","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; Department of Pediatric Hematology\/Oncology, The University of Tokyo, The Institute of Medical Science; The First Department of Pediatrics, Toho University School of Medicine; Departments of Pediatrics at Tokyo Medical and Dental University School of Medicine, Keio University School of Medicine, Juntendo University School of Medicine, Nippon Medical..."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Akira","family":"Ohara","sequence":"additional","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; Department of Pediatric Hematology\/Oncology, The University of Tokyo, The Institute of Medical Science; The First Department of Pediatrics, Toho University School of Medicine; Departments of Pediatrics at Tokyo Medical and Dental University School of Medicine, Keio University School of Medicine, Juntendo University School of Medicine, Nippon Medical..."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yohji","family":"Ohkawa","sequence":"additional","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; Department of Pediatric Hematology\/Oncology, The University of Tokyo, The Institute of Medical Science; The First Department of Pediatrics, Toho University School of Medicine; Departments of Pediatrics at Tokyo Medical and Dental University School of Medicine, Keio University School of Medicine, Juntendo University School of Medicine, Nippon Medical..."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Taijiroh","family":"Mori","sequence":"additional","affiliation":[{"name":"From the Department of OncologyKanagawa Children\u2019s Medical Center, and Department of Pediatrics, Yokohama City University School of Medicine, Yokohama; 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