Rituximab monotherapy for relapsed or refractory primary central nervous system lymphoma

Abstract

2043 Background: Rituximab, a chimeric monoclonal antibody against the CD20 antigen, improves survival when combined with CHOP therapy in patients with systemic diffuse large B-cell lymphoma (DLBCL). Approximately 90% of primary central nervous system lymphomas (PCNSL) are DLBCL and rituximab is now part of combination therapy in some regimens for PCNSL with only anecdotal evidence of efficacy in this patient population. Methods: Adult patients with relapsed or refractory CD20+ PCNSL are being enrolled in a National Cancer Institute-sponsored multicenter phase II trial of rituximab monotherapy in the New Approaches to Brain Tumor Therapy (NABTT) consortium. All patients failed prior methotrexate-based therapy. Rituximab is administered at a dose 375 mg/m2 in weekly intravenous infusions for a maximum of 8 treatments. The primary objectives are to determine the radiographic response proportion, progression-free and overall survival. The study design is a two-stage phase II trial with 15 patients in stage I and 10 additional patients in stage II. Results: Nine patients have been enrolled at the time of this submission. There have been 3 (1 CR, 2 PR) objective radiographic responses in the first 9 patients enrolled. Eight patients have progressed from 3–228 days after treatment and 4 patients have died. The rituximab responses lasted 174 days, 228 days and 324+ days. Four patients have experienced CTC grade 3 or 4 toxicity potentially related to rituximab with adverse events consisting of allergic reaction, fatigue, anxiety and pain. Conclusions: Rituximab monotherapy in patients with relapsed or refractory CD20+ PCNSL results in radiographic regression of tumor in a subset of patients and warrants further study in combination with other chemotherapeutic agents. Enrollment and follow-up are ongoing. No significant financial relationships to disclose.