Radiation Therapy Efficacy and Toxicity for Orbital and Ocular Adnexal Mucosa-Associated Lymphoid Tissue (OAMALT): A Single-Center, Retrospective Study of 32 Cases

PURPOSE: Lymphomas of the orbit and ocular adnexa are histologically heterogeneous and their incidence rate has been increasing lately. However, because of their rarity and diversity, few cases have been analyzed. This study evaluated patients with orbital and ocular adnexal mucosa-associated lymphoid tissue (OAMALT), who received radiotherapy, and categorized their clinical characteristics, treatment outcomes, and complications. PATIENTS AND METHODS: We collected data on clinical presentation, age, sex, imaging, tumor location, treatment methods, pathological diagnosis, cataract incidence, cataract incidence periods, overall survival (OS), and disease-free survival (DFS) from 32 patients with orbital involvement and pathologically confirmed marginal zone B-cell lymphoma of MALT who were treated between 2009 and 2018. Twenty-two patients received 20 Gy/10 Fr using intensity-modulated radiation therapy (IMRT) plus 14 Gy/7 Fr using a 6–14-MeV electron beam therapy using a lens-sparing approach. Ten patients received 32 Gy/16 Fr or 34 Gy/17 Fr using IMRT without the lens shield technique. Kaplan–Meier analysis was used to estimate DFS and OS. RESULTS: The median follow-up time was 83.4 ± 24.5 months. No patient had local recurrence, although three patients developed distant metastases. The 5-year and 10-year OS rates were both 100%. The 5-year and 10-year DFS rates were 96.7% and 74.2%, respectively. Overall, 11 (32.4%) of the 34 lenses developed cataracts. The estimated 5-year, 7-year, and 10-year cumulative cataract rates were 6.9%, 30.9%, and 60.8%, respectively. The median cumulative cataract incidence period was 107.0 months. Age was the only significant parameter associated with cataract formation. CONCLUSION: A radiation dose of 32–34 Gy yields excellent local control, DFS, and OS for OAMALT. Some patients may have systemic relapse, and better identification of these patients is necessary. Reducing the prescription radiation dose or using better radiation techniques to spare the ipsilateral lens could reduce cataract formation.