Radiotherapy may augment response to immunotherapy in metastatic uveal melanoma patients.

Introduction: Uveal melanoma (UM) is a subtype of melanoma arising from the ocular region. Despite various local therapies available, a significant portion of patients develop distant metastases, primarily to the liver. While cutaneous melanoma is very sensitive to immunotherapy, UM is known to be less responsive and patients were excluded from pivotal clinical trials. To date, there is no standard first line therapy for metastatic UM and clinical trial participation is encouraged. While UM is considered a radio-resistant tumor, there is a role for radiotherapy (RT) as palliative treatment and possibly for immune sensitization. This a retrospective analysis aimed at addressing the role of combination checkpoint inhibitors (ICI) with RT as a synergistic treatment in metastatic UM patient. We hypothesized that concurrent RT would improve the clinical response to immunotherapy. Methods: Retrospective chart review of patients with metastatic UM treated with ICI at Ella Lemelbaum Institute between 2015 and 2021. Patients' electronic medical records were analyzed for baseline characteristics, response rate and survival data. Patients were grouped according to receipt of concomitant RT. Study was approved by local IRB and statistical analyses done using Stata V.17. Results: Thirty-nine patients were treated with immunotherapy. Fifty percent were treated with anti-programmed cell death (PD)-1 and 50% with anti-PD1- anti CTLA4 combination therapy. Nine patients were treated concomitantly with immunotherapy and external beam RT or with stereotactic body RT (group A) and 29 patients were treated with immunotherapy alone (group B). Overall response rate was significantly higher in group A (44% versus 10%, p = 0.004). Median progression-free survival was longer for patients in group A (22 months versus 3 m, Hazard Ratio (HR) = 0.37, p = 0.036). Median overall survival was also longer for group A (26 months versus 7.5 m, HR = 0.34, p = 0.03). Toxicity was comparable between the groups. Conclusions: RT may improve response to immunotherapy with ICI in metastatic UM patients and may confer an advantage in survival. Further prospective, larger studies are warranted.