The outcome of radiation therapy as a primary treatment in orbital lymphoma: a systematic review

BACKGROUND: The extranodal marginal-zone B-cell lymphomas of mucosa-associated lymphoid tissue (MALT) is the most common orbital and adnexal lymphomas. Radiotherapy is one of the most preferred treatment options for orbital lymphomas since they are localized and radiation sensitive. The objective of this study is to evaluate how radiation therapy affected the outcome of orbital MALT lymphoma. MATERIALS AND METHODS: PRISMA guideline was used to conduct this systematic review of electronic databases (PubMed, EMBASE and Cochrane Library), then we assessed the quality of evidence of each paper. RESULTS: Twenty-five studies were finally included. 94% studies were intended for definitive therapy and almost all of the studies used external radiation sources. The total doses given to the tumor bed ranged from 4 Gy to 55 Gy and were divided into three groups: ultra-low dose (4–6 Gy), standard-dose (24–30.6 Gy), and high-dose (> 30.6 Gy). 75–90% patients showed CR and local relapse was only reported at 3.5–5%. Higher 5-year PFS was reported in the patients group with lens shielding (90.1% vs. 82.1%) and an increase in Meiboscore after RT courses. Toxicities, including dry eye and cataract, were reported in several patients. Acute toxicities subsided gradually over a few months with artificial tears. The risk of early cataract formation increases in patients who received > 30 Gy and lower in the IMRT group. CONCLUSION: RT is a successful primary definitive therapy for low-grade orbital MALT lymphoma, with a high survival rate, low recurrence rate, and typically acceptable toxicity.