Clinical Characteristics and Treatment Outcomes of Patients with Primary Ocular Adnexal Lymphoma at Siriraj Hospital

Objective: Malignant lymphoma represents the most common primary orbital malignant neoplasm. 
Materials and Methods: We retrospectively reviewed data and analyzed clinical characteristics and treatment outcomes of patients with primary ocular adnexal lymphoma at Siriraj Hospital, a tertiary health-care and teaching center in Bangkok, Thailand between January 2004 and June 2017. 
Results: From the total of 94 patients with primary ocular adnexal lymphoma, 77 cases (81.9%) were indolent, of which extranodal marginal zone lymphoma (EMZL) was the most common (76.6%). Aggressive subtype accounted for 17 cases (18.1%), consisting of diffuse large B-cell lymphoma (9.6%), mantle cell lymphoma (4.3%), and extranodal NK/T cell lymphoma (3.2%). Plasmacytic differentiation was found in half of EMZL and 4 cases of EMZL had association with IgG4-related disease. Most of the patients presented with proptosis (54.3%), followed by a palpable mass (42.6%). Most patients had Ann Arbor stage I (66.3%) with zero ECOG performance status (91.1%). Chemotherapy was the main treatment for both indolent and aggressive lymphomas. The overall response rate and complete response rate were 88.6% and 68.7%, respectively. The 5-year progression-free survival (PFS) and overall survival (OS) rates were 60.1% and 84.2%, respectively. The indolent group had better overall (92.4% vs 69.2%) (P=0.01) and complete response rates (73.1% vs 50%) (P=0.01) than the aggressive group. 
Conclusion: Histopathological subtypes and clinical stages of lymphoma are the best indicators of prognosis and treatment outcomes. Chemotherapy was an effective treatment modality for both indolent and aggressive lymphoma subtypes with better treatment outcomes in the indolent group.