Efficacy and Safety Study of Rituximab, Methotrexate and Lenalidomide Chemotherapy（R2-MTX） in Newly Diagnosed Primary Central Nervous System Lymphoma：a Single Arm, Multicenter, Phase 2 Study

This is a single arm, multicenter, phase 2 study designed to evaluate the efficacy and safety of rituximab, methotrexate and lenalidomide as first-line regimens in the treatment of newly primary central nervous system lymphoma. A total of 40 patients plan to participate in this study to receive a total 6 cycles of induction chemotherapy followed by 4 cycles of maintenance chemotherapy. Follow-ups should be taken up to the first 3 years. The primary endpoint is objective response rate (ORR) and secondary endpoint includes Progression free survival (PFS), overall survival (OS), and adverse events.