Localized Orbital Adnexal Mucosa-Associated Lymphoid Tissue Lymphoma Treated With Radiation And Rituximab: A Single Institute Experience.

e19034 Background: Standard treatment for patients with orbital mucosa-associated lymphoid tissue (MALT) lymphoma is not established due to paucity of prospective trials, small numbers of patients in published studies, heterogeneity of treatment and short follow up. Local radiation therapy provides excellent disease control but delayed relapses are common. At our institute, we aimed to further decrease the risk of delayed relapse by combining rituximab with radiation. Rituximab is active in marginal zone lymphoma and it may sensitize lymphoma cells to radiation and treat occult systemic disease. Methods: We retrospectively reviewed records of 10 consecutive evaluable patients treated between 1997 and 2015. All had biopsy-proven MALT lymphoma. Median age was 64 years (range 37-92 years). Seven were female and 3 were male. Median duration of symptoms before diagnosis was 6.0 months (range 2 - 24 months). Patients underwent staging including full body PET with diagnostic CT scan and MRI of the orbits. Nine had stage 1E disease and one had stage IIE disease. All patients received radiation, median dose is 36.00 Gy (range 30.60-39.60 Gy). Six received rituximab 375 mg/m2 weekly for 4 doses starting at least one week before radiation. Results: Median follow up duration was 5.8 years (range 0.2-8.0 years). Only one of 10 patients died (from transformation to aggressive large cell lymphoma). Nine patients had complete remission and one had partial remission. One of 6 patients treated with rituximab and radiation and 3 of 4 treated with radiation alone relapsed. Median time to relapse was 4.8 years (range 3.2-11.0 years). All relapsing patients received second line treatment. One patient developed cataract needing surgery and another developed retinopathy requiring steroid injections. Conclusions: In this series of primary orbital MALT lymphoma, radiation combined with rituximab was well tolerated and associated with long-term disease-free survival as compared to radiation alone. This combination therapy should be evaluated in prospective studies with more than 5 year follow up to capture late relapse.