Radiotherapy of localized orbital mantle cell lymphoma: a SEER database analysis of long-term outcomes.

[INTRODUCTION] Primary orbital lymphomas are predominantly low-grade subtypes, such as extranodal marginal zone lymphomas (MALT) and follicular lymphomas, which are highly radiosensitive. Mantle cell lymphoma (MCL), although less common, is an aggressive high-grade subtype with an intermediate-to-poor prognosis. While systemic therapies are standard for MCL, data on the efficacy of radiotherapy in localized orbital MCL are limited. This study evaluates the long-term outcomes of radiotherapy for localized orbital MCL using the Surveillance, Epidemiology, and End Results (SEER) database.

[MATERIALS AND METHODS] This retrospective study analyzed cases of localized orbital MCL treated with radiotherapy between 2000 and 2021 identified in the SEER database. Demographic, clinical, and survival data were extracted. The primary endpoints were overall (OS) and cancer-specific survival (CSS), estimated using the Kapla-Meier method and Cox proportional hazards models. Statistical analyses were conducted using R software (R Foundation, Vienna, Austria), with a significance threshold set at p < 0.05.

[RESULTS] Among 13,662 patients with localized primary orbital lymphomas, 63 (0.5%) cases were histologically confirmed as MCL. Of these, 35 patients (55.6%) received radiotherapy. The age-adjusted incidence rate of orbital MCL was 0.033 per 1,000,000 person-years (95% CI: 0.025-0.042). Patients were predominantly elderly (42.9% were over 80 years old) and male (male-to-female ratio of 2.18 : 1; p = 0.012). With a median follow-up of 91 months (range: 4-237 months), the median OS was 113 months. The 5‑, 10-, and 15-year OS rates were 76.5% (95% CI: 62.7-93.4%), 48.2% (32.9%-70.6%), and 42.8% (27.4%-66.9%), respectively. Median CSS was not reached, with 5‑, 10-, and 15-year CSS rates of 98.0% (95% CI: 78.0-100.0%), 83.4% (69.5%-100.0%), and 83.4% (69.5%-100.0%), respectively. Chemotherapy did not show a significant impact on survival.

[CONCLUSION] Radiotherapy achieves excellent long-term survival outcomes for localized orbital MCL, particularly in elderly and frail patients who may not tolerate systemic therapies. These findings support radiotherapy as an effective therapeutic option for this rare lymphoma subtype. Future multicenter studies are warranted to optimize radiotherapy protocols and improve patient outcomes.