Rituximab and Yttrium-90 Ibritumomab Tiuxetan Radioimmunotherapy May Be Feasible Options in Patients with Low-Grade Lymphoma of the Orbit.

Objective: To report a cohort of patients with lymphoid tumors of the orbit, including 1 with benign lymphoid hyperplasia of the orbit whose disease responded to immunotherapy with rituximab alone or rituximab followed by Zevalin (yttrium-90 ibritumomab tiuxetan) radioimmunotherapy.

Methods: Between October 2002 and January 2005, 8 patients with low-grade non-Hodgkin’s lymphoma and 1 with benign lymphoid hyperplasia of the orbit were treated with monoclonal antibodies against CD20. Five patients with low-grade lymphoma of the orbit (3 with follicular B cell or 2 with MALT) received rituximab followed by yttrium-90 ibritumomab tiuxetan, 2 patients with low-grade orbital lymphoma (1 with follicular B-cell and the other with small lymphocytic lymphoma) and 1 patient with benign lymphoid hyperplasia received rituximab alone. Three out of the 5 patients who received yttrium-90 ibritumomab tiuxetan were part of a prospective trial evaluating the efficacy of yttrium-90 ibritumomab tiuxetan for low-grade B-cell lymphoma of the orbit; the other 2 had been treated in other open label trials at M. D. Anderson Cancer Center. For each patient, clinical records and imaging studies were reviewed to establish the diagnosis and document response.

Results: Three men and 5 women in this cohort were between the age of 23 and 83 years old (median age, 63 years). Of the 7 patients with orbital lymphoma, 4 had stage IE and the other 3 had stage IVE, and 6 had previously untreated disease. All 8 patients experienced resolution of the orbital tumor in response to treatment with monoclonal antibodies against CD20. Follow-up time ranged from 6 months to 32 months (mean, 12 months) after completion of immunotherapy. There were no serious systemic or ocular side effects during the study period. The most commonly experienced side effect was mild fatigue. All 5 patients treated with yttrium-90 ibritumomab tiuxetan had transient pancytopenia, which normalized as expected within 3 months after treatment. One patient who received yttrium-90 ibritumomab tiuxetan developed shingles 6 weeks after treatment. There were no sequelae from this infection, which resolved with the usual course of oral antiviral therapy.

Conclusions: Rituximab and yttrium-90 ibritumomab tiuxetan may be considered as alternative treatment modalities to external beam radiation therapy for low-grade B-cell follicular non-Hodgkin’s lymphoma or MALT of the orbit. Systemic targeted immunotherapy may potentially have the advantage of lower rate of distant (out-of-field) relapse and less ocular toxicity compared with external beam radiotherapy; these potential advantages would have to be verified in long-term studies and in larger numbers of patients.