Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) ALL-T11 and Japan Adult Leukemia Study Group (JALSG) T-ALL-211-U ALL-T11: a Multi-Center Phase II Study in Children and Adolescence with Newly Diagnosed T-cell Acute Lymphoblastic Leukemia

INTERVENTION: Stratification(SR/HR/VHR) based on early prednisolone response, remission induction at time‐point1(TP1) and MRD at time‐point2(TP2). SR: Early prednisolone good responder (PGR), Time‐point1(TP1):BM=M1 and TP2:MRD<10*‐3 . Clinical study question: safety and effectiveness of BFM‐MR regimen with intensive L‐asp and without Nelarabine. HR: Early prednisolone poor responder (PPR), TP1:BM=M1 and TP2:MRD<10*‐3 . Clinical study question: safety and effectiveness of BFM‐HR regimen with intensive L‐asp and Nelarabine. VHR: TP1:BM=M1 and TP2:MRD>=10*‐3 or TP1:BM=M2/M3 and TP2:BM=M1. Clinical study question: rondamization ; BFM‐HR block regimen vs high‐dose dexamethazine containing regimen. CONDITION: T‐cell Acute Lymphoblastic Leukemia PRIMARY OUTCOME: 1) 3 years event free survival; 2) MRD disappearance of VHR group in RCT SECONDARY OUTCOME: 1) Overall survival (OS); 2) Remission induction rate; 3) Adverse event (including acute and late effect of patients diagnosed at less than 18 years old) INCLUSION CRITERIA: 1) diagnosis of T‐ALL (CD3+ or cyCD3+ and more than one is positive among CD2, CD5, CD7, CD8) 2) age less than 25 years old 3) ECOG performance status (PS) acore of 0‐3 4) no history of previous chemotherapy or radiation therapy 5) sufficient hepatic and renal function satisfying the laboratory data listed below ; (1) T‐Bili: within 3x of age adjusted upper‐limit of normal range. (2) Creatinine: within 3x of age adjusted upper‐limit of normal range. 6) written informed consent obtained from patient or guardians.