Adjuvant Lymph Node Radiotherapy and Immunotherapy in Stage III Melanoma.

With the promising results of immunotherapy (IT) in patients with stage III melanoma, the role of adjuvant radiotherapy (RT) after resection and complete lymph-node dissection (CLND) must be reassessed. We evaluate outcomes and safety of adjuvant RT and IT versus IT only in patients with resected stage III melanoma (AJCC 8th edition). This retrospective and single institution study included all consecutive patients treated for a stage III melanoma with CLND and adjuvant IT (anti-PD1) from January 2019 to December 2022. The radiotherapy associated with immunotherapy (RT+IT) group was defined by completion of IT and adjuvant RT in the lymph-node dissection area. The primary endpoint was disease-free survival (DFS). The secondaries endpoints were locoregional (lymph-node field) progression (LRR), incidence of adverse events ≥ grade 3 according to Common Terminology Criteria for Adverse Events (CTCAE) and DFS in patients with high risk of locoregional recurrence. Thirty-three patients were included and all received adjuvant IT (pembrolizumab or nivolumab). Among them, twelve received adjuvant lymph-node field radiotherapy. The median duration of follow-up was 17 months (8-45). Patients in RT+IT group had a significantly higher disease stage and more frequent extracapsular extension. At 12 months, the disease-free survival was 66.7% (95% IC: 42.5-82.5) for the IT group and 83.3% (95% IC: 48.2-95.6) for the RT+IT group (p = 0.131). After multivariate analysis, compared to patients with IT treatment, the hazard ratio (HR) was 0.216 ([0.0481, 0.965], p<0.05) for patients treated with RT+IT. The locoregional progression rates were respectively 24% and 8% in patients for which treatment was IT and RT+IT (p = 0.379). After surgery, 21% of patients presented with ≥ grade 3 adverse events. After adjuvant treatment, 6% of patients developed ≥ grade 3 immunotherapy-related events and none developed ≥ grade 3 radiation-related adverse events. In patients with resected stage III melanoma (AJCC 8th edition), adjuvant lymph-node field radiotherapy combined with immunotherapy seems to be associated with longer disease-free survival, with acceptable tolerance. However, these results need to be confirmed by long-term and prospective studies. [ABSTRACT FROM AUTHOR]