Partial orbit irradiation achieves excellent outcomes for primary orbital lymphoma.

PURPOSE: Primary radiation therapy (RT) achieves excellent local control and overall survival when treating localized orbital lymphoma. However, evidence supporting irradiation of partial orbit volumes to spare nearby critical structures is lacking. We sought to investigate outcomes for patients with localized orbital lymphoma treated with partial orbit irradiation.

METHODS AND MATERIALS: We retrospectively reviewed patients with orbital lymphoma treated with RT at our institution who met our inclusion criteria: biopsy-confirmed, low-grade lymphoma, localized disease, partial orbit treatment volumes, and follow-up >3months. The Kaplan-Meier method was used to measure overall survival (OS), and the cumulative incidence function adjusted for the competing risk of death was used to measure local failure (LF), contralateral orbit recurrence (COR), and progression. Patient characteristics were compared with outcomes using Fisher exact test for dichotomous variables and Wilcoxon rank-sum test for continuous variables.

RESULTS: Thirty-two patients meeting inclusion criteria were identified with median follow-up of 45.8months (range, 3.6-171.9). The majority had stage IEA disease; their sites included conjunctiva (n=20) and retrobulbar or lacrimal gland (n=12). Median partial orbit RT dose was 30.6Gy (range, 22.5-36). Five-year OS was 100%. Five-year cumulative incidence of LF, COR, and overall disease progression was 5.3%, 5.9%, and 21.4%, respectively. Five-year cumulative incidence of LF was 8.3% for conjunctival disease versus 0.0% for retrobulbar or lacrimal gland involvement (P=.15). No significant association was observed between the outcomes of LF, COR, or progression and pretreatment characteristics. Acute and late toxicity included grade 2 periorbital edema (n=3, 9.4%), dry eye (n=3, 9.4%), retinal vascular disorder (n=1, 3.1%), conjunctivitis (n=2, 6.3%), and grade 3 cataract (n=1, 3.1%).

CONCLUSIONS: Use of partial orbit irradiation in treating low-grade, localized orbital lymphoma achieves excellent survival with low rates of LF, COR, or progression.