Initial Experience with Rituximab and 90Y-Ibritumomab Tiuxetan for the Treatment of Mature B-Cell Lymphoma.

Introduction: Rituximab and 90Y-ibritumomab tiuxetan constitute a relatively new radioimmunotherapeutic regimen for patients with CD20 low-grade non-Hodgkin’s lymphoma (NHL).

Methods and Results: We have so far treated 9 patients, with mature CD 20 positive B-cell lymphoma, according to a standard protocol of Zevalin. All patients received 250 mg m² of cold rituxemab infusion over 2 hours followed 7 days later by the same infusion of rituxemab plus within 4 hours by IV Y90 -ibritumomab tiuxetan (3– 4 microCuri/kg depending upon platelet counts). Labeling of cold antibody with Y90 was carried out and tested for quality prior to administration on the day of therapy. There were 4 male & 5 females with a mean age of 59.13 + 5.7 years. All patients except one had been previously treated with cold tiuxetan as part of standard chemotherapy (R-CHOP, R-DHAP, R-CVP, R-Cholorambucil). Five patients had follicular lymphoma grade I, II or III. Three out 5 of these patients were treated with Zevalin after a mean period of 4.26 years from diagnosis after failing 2^nd line therapy (2 patients) or with significant residual disease thereafter (one patient). 1 patient with Follicular lymphoma grade III was treated with Zevalin 22 years 3 months after initial diagnosis who was progressing after 2^nd line chemotherapy, and one patient with Follicular lymphoma grade I who had significant residual disease 7 months post first line therapy. two patients had diffuse large B-cell Lymphoma. One treated with Zevalin 9 months after initial diagnosis and failing first line therapy and significant residual disease following 2^nd line therapy, the other receiving Zevalin 6 months of initial diagnosis, as consolidation therapy following minimal residual disease after first line chemotherapy. 1 patient with Nodal Marginal Zone B-cell Lymphoma was treated 2 years 7 months after initial diagnosis who had significant residual disease after 2^nd line chemotherapy. The last patient with mantel cell lymphoma was treated 2 years 7 months after initial diagnosis with Zevalin who had significant residual disease following first line chemotherapy. All patients were followed weekly for 2 months after initial therapy with Zevalin to monitor hematological toxicity and at 3 months interval with follow up CT scans to monitor response to therapy.

Patients are under follow up after Zevalin therapy now for a mean period of 0.77 + 0.44 years (range1 year 4 months to 1 month). 3 patients suffered from sever thrombocytopenia and severe neutropenia requiring supportive treatment, rest of the patient had moderate to sever hematological toxicity requiring no treatment. Response to therapy was judged according to well known international criteria based on serial CT scans, although gallium 67 and MRI scans were also done in selective cases. Three patients were in complete remission, 3 patients had good response to therapy with more than 75 % reduction in tumor volume, and 2 patients have not yet been evaluated for response to therapy. The only remaining patient with mantel cell lymphoma had good response at 2 months with progression after 8 months.

Conclusion: Radioimmunotherapy is an effective and a feasible treatment option for the management of lymphoid malignancies.