Rituximab for Treatment of Advanced Extranodal Marginal Zone B Cell Lymphoma of the Mucosa-Associated Lymphoid Tissue Lymphoma

BACKGROUND: Extranodal marginal zone B cell lymphoma of the mucosa-associated lymphoid tissue (MALT) is a relatively common type of lymphoma. Owing to its B cell lineage, it appears to be a potential target for treatment with the CD20 antibody rituximab. We present an analysis of our experience with rituximab for treatment of patients with advanced MALT lymphoma. PATIENTS AND METHODS: A retrospective analysis of patients with histologically verified MALT lymphoma undergoing treatment with rituximab was done. After reassessment of histological samples for the presence of MALT lymphoma, patients were evaluated as regards date of diagnosis, prior therapy for MALT lymphoma, sites of involvement upon treatment with rituximab, clinical response in terms of complete remission (CR), partial response (PR), stable disease (SD) and progressive disease as well as symptomatic response, duration of response and survival. RESULTS: A total of 9 patients with advanced MALT lymphoma undergoing therapy with single-agent rituximab were identified. All patients received treatment at a dose of 375 mg/m(2) once weekly x4. One patient each had relapsed after chemotherapy and radiation, respectively, while none of the other 7 patients had received prior cytotoxic treatment or radiation. Three patients achieved a CR, 2 patients had PR for 6 and 14 months, while the remaining patients had SD between 8 and 18+ months. One patient died of progressive disease in spite of the initiation of chemotherapy and 1 patient succumbed to a cardiovascular event while having been in ongoing PR for 11 months. The other 7 patients are currently alive with disease 10-27 months after initiation of therapy. Follow-up biopsies for histological assessment were available in 5 patients with gastric lymphoma. In 1 patient with SD, however, persistence of CD20-positive cells within lymphoepithelial lesions was noted in spite of almost complete depletion of B lymphocytes from the normal gastric mucosa, suggesting either recirculation of MALT lymphoma cells to these lesions or defining lymphoepithelial lesions as a sanctuary site from rituximab penetration. CONCLUSION: Rituximab had only moderate activity in terms of inducing objective responses in our unselected and heterogeneous cohort of patients with disseminated MALT lymphoma. Long-term disease stabilization, however, along with a symptomatic benefit was seen in all patients. Our data nevertheless indicate that rituximab might not optimally penetrate into the gastric mucosa in all patients.