In this prospective, phase III, multicenter, randomized, controlled study, the investigatirs aim to compare the efficacy of intravenous MTX(IV arm) at a dose of 1g/m2 with intrathecal MTX(IT arm) in terms of preventing CNS relapse. All the patients will recieve RCHOP regimen as front-line treatment of DLBCL. Patients in IV arm will recieve 4 course of IV MTX, which is incorporated into the RCHOP, naming R-MTX-CHOP regimen. Patients in IT arm will be given intrathecal MTX for 4 courses (one time for each course). 2 year CNS relapse rate is the primary endpoint while 2 year PFS, 2 year OS and safety are the secondary endpoint.
