Orbital marginal zone B-cell lymphoma of MALT: Radiotherapy results and clinical behavior

Purpose: To elucidate the clinical behavior and treatment outcome of low-grade primary orbital lymphoma arising from mucosa-associated lymphoid tissue (MALT). Methods and Materials: Forty-eight patients with pathologically confirmed marginal zone B-cell lymphoma of MALT were treated with radiotherapy (RT). Thirty-eight patients (79.1%) received thorough staging workup studies including bone marrow biopsy. Radiation doses ranged from 5.4 to 30.6 Gy (median, 30.6 Gy). Median follow-up period was 70 months. Results: Only 2 patients revealed extraorbital lymphoma involvement (bone marrow, skin). Forty-six of 52 eye lesions showed complete response to RT. Six lesions demonstrated a partial response and showed gradual regression during the follow-up period of 39-72 months. Three patients experienced local recurrences at 34, 48, and 52 months after RT, which seemed to be related to improper use of the lens shield. Salvage re-RT was successful. The 10-year actuarial relapse-free survival, cause-specific survival, and overall survival rates were 93.1%, 97.9%, and 86.9%, respectively. Conclusion: Most of the MALT lymphoma of the orbit was localized at diagnosis and extraorbital relapse rarely occurred. Therefore, extensive staging workup at the time of diagnosis and follow-up studies to detect distant relapse may not be obligatory. Low-dose RT alone with proper lens shielding is the optimum treatment modality for orbital MALT lymphoma.