Rituximab-induced tumor progression: does it really happen?

Monoclonal antibodies have been gaining a wide role in the treatment of malignant diseases. A human chimeric anti-CD20 monoclonal antibody (Mab) rituximab (Rituxan in USA; Mabthera in Europe) was approved for the treatment of refractory or relapsed low-grade or follicular non-Hodgkin's lymphoma (NHL) in 1997 (1-3). Rituximab has efficacy in other refractory CD20+ NHLs, hairy cell leukemia, plasma cell dyscrasias, posttransplant lymphoproliferative syndrome, autoimmune phenomena such as refractory hemo lytic anemias, and immune thrombocytopenias (4-8). Its combination with standard chemotherapy protocols for NHL has been investigated thoroughly owing to its synergistic effect when combined with chemotherapeutic agents (3). Coiffier et al. recently published a randomized trial showing a statistically significant survival benefit of rituximab-CHOP combination over CHOP alone in elderly patients with diffuse large-B-cell lymphoma (9,10). In addition to these widening beneficial therapeutic effects, rituximab has well-known side effects, encountered especially during its first infusion, such as chills, fever, allergic reactions, cardiopulmonary syndrome, and tumor lysis syndrome. We would like to share our clinical observation in a patient with NHL, whose disease seemed to go into an accelerated progression phase after rituximab administration.