Treatment of Acute Lymphoblastic Leukemia in the Tokyo Children's Cancer Study Group—Preliminary Results of L84-11 Protocol

The Tokyo Children's Cancer Study Group (TCCSG) has performed prospective randomized controlled studies since 1984 for childhood acute lymphoblastic leukemia (ALL). Four hundred and ninety-eight newly diagnosed patients were treated with 5 different regimens designated as S1, S2 for a standard risk group (SRG), H1 and H2 for a high risk group (HRG) and HEX for an extremely high risk group of patients. We added intermediate-dose methotrexate as early intensification therapy in the S2 and H2 groups to reduce extramedullary and medullary relapses. Event-free survival of all patients at 4 years 6 months from the start of this regimen (median follow-up period 32 months) was 67.5%. The CNS relapse rate was significantly decreased to 2.2% compared to previously reported studies and our own experience. There were some unexpected complications of the CNS such as myelopathy and/or leukoencephalopathy. For the SRG early ID-MTX seemed to be useful to improve the prognosis, but triple intrathecal injections (TIT) should be limited in number. The 24Gy cranial irradiation (CRX) was effective but possibly excessive for the HRG. As evidenced by the success of the HEX group regimen, more intensive multi-drug consolidation in the early post-remission phase might be necessary to improve further the prognosis and to make it possible to shorten the treatment periods.