Table 2.

Differential dosing of high-dose MTX based on risk stratification

BFM risk group	MTX dose	Infusion time, h	FAB/LMB risk group	MTX dose	Infusion time, h
R1: stage I/II resected	1000 mg/m2 × 2	4	Group A: stage I/II resected	None	None
R2: unresected stage I/II, stage III with low LDH	1000 mg/m2 × 4	4	Group B low risk: not in groups A or C, low LDH	3000 mg/m2 × 4	3
R3: stage III and CNS− stage IV with intermediate LDH	5000 mg/m2 × 4*	24	Group B high risk: not in groups A or C, high LDH	3000 mg/m2 × 4	3
R4: stage III/IV with high LDH or any CNS+ stage IV	5000 mg/m2 × 4*	24	Group C: bone marrow ≥ 25% and/or CNS+	8000 mg/m2 × 3*	4 for CSF−and 24 for CSF+

CSF⁺ is defined by the presence of blasts on CSF cytology. LDH thresholds for BFM: low is <2 times the upper limit of normal (ULN), intermediate is 2 to 4 times the ULN, high is >4 times the ULN. LDH thresholds for FAB/LMB: low LDH is <2 times the ULN, and high LDH is >2 times the ULN.

^*Patients in risk groups R3, R4, and C also received high-dose cytarabine.