Combination of rituximab and oral melphalan and prednisone in newly diagnosed multiple myeloma.

Clonotypic B lymphocytes may underlie relapse of patients with multiple myeloma. Rituximab, a CD20 monoclonal antibody, may result in eradication of the monoclonal B cells. We conducted a phase II study of rituximab in combination with melphalan and prednisone therapy (MP) followed by rituximab maintenance in newly diagnosed multiple myeloma patients. Sixteen patients (35%) had CD20 positive bone marrow plasma cells, while 9 patients (20%) had unknown CD20 status. No patient had a complete remission, 26 patients (58%) had a partial response, 6 patients (13%) had a minimal response, and 8 patients (18%) had stable disease. The median event-free survival was 14 months, and the 7-year overall survival was 30%. The toxicity of the combination was overall manageable and consistent with what is generally noted with MP chemotherapy. The combination of rituximab to MP therapy did not result in improved response rate or event-free survival.