Ultra-low dose radiotherapy in the management of low-grade orbital lymphomas.

Background: Ultra-low dose radiotherapy (ULDRT) (2 × 2 Gy) has been used for symptomatic control of low-grade lymphomas with surprising local control rates, suggesting that these entities could respond to lower doses. These are particularly desirable for the treatment of orbital sites and some publications refer to high rates of complete responses. In this paper, we present our experience with the use of ULDRT for indolent orbital lymphomas. Materials and methods: Electronic files and treatment plans of patients treated with ULDRT for low-grade orbital lymphoma were retrospectively reviewed. Oncological outcomes and toxicities were collected and described for each patient. Results: Seven patients (median age of 75 years) with 8 lesions (3 follicular, 2 MALT, 1 marginal and 1 low-grade non-Hodgkin lymphoma) were considered for analysis. The majority had stage IE disease and one patient had bilateral disease. Six tumors were detected on imaging (median size of 20 mm). Involved orbital sites were periocular, conjunctival and palpebral; there was one case of intraocular (choroid) and one case of lacrimal gland involvement. One patient received consolidative rituximab after RT. The median follow-up time was 22 months. Two patients had partial response, one of them with persistent minimal choroidal disease and the other with partial response on CT. Five (71%) patients had clinical (n = 2) or radiologic (n = 3) complete response on treated sites. Reported late toxicities were minimal and included dry eye and pruritus. Conclusion: In our experience, ULDRT achieved a local control rate of 100% and complete response rate of 71% with minimal toxicity.