Treatment of Primary CNS Lymphoma with Induction High-Dose Methotrexate, Temozolomide, Rituximab Followed by Consolidation Cytarabine/Etoposide: A Pilot Study with Biomarker Analysis.

Background: There is no consensus on the optimal treatment for patients diagnosed with primary CNS lymphoma (PCNSL). The goals of this study were:

1. to determine the safety and efficacy of a methotrexate (MTX)-based induction therapy followed by high-dose consolidation chemotherapy and the elimination or deferral of whole brain irradiation,

2. to identify molecular markers in PCNSL which predict sensitivity to chemotherapy and outcome.

Methods: 23 newly diagnosed, CD20-positive, immunocompetent PCNSL patients were treated with combination high-dose intravenous MTX (8 gm/m²), temozolomide (150 mg/m²/day) and intravenous rituximab (375 mg/m²) (MTR). Patients in complete remission (CR) after eight courses of MTX were offered consolidation with high-dose cytarabine (2 g/m² x 8 doses) and etoposide (40 mg/kg over 96 hours) (AE). Candidate markers of outcome in PCNSL were identified by gene expression profile analysis of an independent, multicenter dataset of PCNSL tumors. Immunohistochemical analysis of one of these markers, death-associated protein-1 (DAP-1), was performed on paraffin sections of tumors from 18 of the patients treated with the MTR regimen.

Results: MTR induction followed by AE consolidation was well tolerated with no treatment-related mortality or evidence for neurotoxicity. Thirteen patients (56.5%) attained CR with induction; 8 received consolidation; 5 in CR refused AE. Median progression-free (PFS) and overall survival (OS) has not yet been reached with a median follow-up of 33 months. Karnovsky performance status (KPS) correlated with improved survival (p<0.0281). Expression by lymphoma cells of DAP-1, a regulator of apoptosis, was associated with improved progression-free survival (p<0.03) and overall survival (p<0.038).

Conclusions: Combination MTR followed by AE is well tolerated in PCNSL. PFS appears at least similar to regimens that contain whole brain irradiation. A multi-center study has been initiated to further evaluate this regimen. DAP-1 may be a tumor suppressor whose expression in PCNSL predicts a favorable response to MTX-based therapy.