High-Dose (HD) Methotrexate (MTX) Induction Chemotherapy Followed by Alternative HD MTX-based and HD Cytarabine-based Combination Consolidation Chemotherapy for Newly Diagnosed Primary CNS Lymphoma; CISL 10-01 Study

Inclusion criteria 1. Histologically confirmed Primary Central Nervous System (CNS) lymphoma 2. Previously untreated. Patients treated with steroid alone are eligible. 3. Performance status: ECOG 0-3. 4. Age; 20-70 5. Adequate renal function: Estimated glomerular filtration rate (GFR) or estimated creatinine clearance (CrCl) ≥ 50 mL/min 6. Adequate liver functions: Transaminase (AST/ALT) \< 3 X upper normal value \& Bilirubin \< 2 X upper normal value 7. Adequate hematological function: hemoglobin ≥ 9 g/dL absolute neutrophil count (ANC) ≥ 1,500/μL and platelet count ≥ 75,000/μL 8. At least one cerebral mass lesion on magnetic resonance imaging (MRI) without involvement beyond the central nervous system (CNS) 9. Life expectancy \> 6 months 10. A negative serum or urine pregnancy test prior to treatment must be available both for pre menopausal women and for women who are \< 1 years after the onset of menopause. 11. Informed consent Exclusion criteria 1. Other subtypes NHL than Primary Central Nervous System (CNS) lymphoma 2. Systemic involvement of Primary CNS lymphoma except leptomeningeal involvement 3. Intraocular lymphoma 4. HIV (+) 5. Any other malignancies within the past 5 years except curatively treated non-melanoma skin cancer or in situ carcinoma of cervix uteri 6. Pregnant or lactating women, women of childbearing potential not employing adequate contraception 7. Other serious illness or medical conditions * Unstable cardiac disease despite treatment, myocardial infarction within 6 months prior to study entry * History of significant neurological or psychiatric disorders * Active uncontrolled infection (viral, bacterial or fungal infection) 8. Patients who have HBV (+) are eligible. However, primary prophylaxis using antiviral agents (i.e. lamivudine) is recommended for HBV carrier to prevent HBV reactivation during whole treatment period. 9. Concomitant administration of any other experimental drug under investigation, or concomitant chemotherapy, hormonal therapy, or immunotherapy.