Maintenance Obinutuzumab in Treating Patients With Central Nervous System Lymphoma Who Have Achieved a Complete or Partial Response

PRIMARY OBJECTIVE: I. To determine the effect of maintenance obinutuzumab on duration of response (partial response \[PR\] or complete response \[CR\]) in patients with CD20+ B-cell primary central nervous system lymphoma (PCNSL) who attain PR or CR to first-line treatment with high-dose methotrexate-based chemotherapy. SECONDARY OBJECTIVES: I. To evaluate overall survival after PR or CR (overall survival \[OS\]-PRCR). II. To evaluate neurocognitive function, quality of life, and neuroimaging as indicators of neurotoxicity. III. Progression-free survival (PFS) and overall survival (OS) will be calculated. OUTLINE: Patients are randomized to 1 of 2 treatment arms. ARM I (MAINTENANCE THERAPY): Patients receive obinutuzumab intravenously (IV) on days 1 and 2 for the first cycle, and on day 1 for the subsequent cycles. Cycles repeat every 60 days for 2 years in the absence of disease progression or unacceptable toxicity. ARM II (OBSERVATION): Patients undergo observation for a total of 2 years.