ESTRO 2025 - Abstract Book

S1668

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

Purpose/Objective: Cutaneous squamous cell carcinoma (cSCC) is a common malignancy, typically treated with surgery. Despite surgery’s effectiveness, about 5% of cases present high-risk features such as regional nodal metastases. Post operative radiation therapy (PORT) improves outcomes for high-risk patients, but the TROG 05.01 trial found no added benefit of concurrent chemoradiotherapy. (1) This secondary analysis seeks to identify patients with poor disease-free survival (DFS) to assess the potential role of further adjuvant treatment intensification, such as immunotherapy. Material/Methods: The study included patients from the TROG 05.01 trial. The primary objective of this trial was to identify a low DFS subgroup following PORT with or without concurrent carboplatin-based chemotherapy and report overall survival for this group. Recursive partitioning using Classification and Regression Trees (CART) with cross-validation was used to identified prognostic subgroups. Cox regression was used to estimate the hazard ratio (HR) between groups. Results: Three hundred twenty-one patients were randomly assigned to the TROG 05.01 trial with 310 patients commencing allocated adjuvant treatment. The regression tree identified 6 leaf nodes, categorising DFS into three risk groups, (high, intermediate, and low risk). Cross-validation confirmed the high-risk group but not the lower risk groups. High-risk patients (n=88) were patients with extra nodal extension (ENE), and nodal size of 22mm or greater. All other patients were considered not high-risk. The 5-year DFS and OS was 56% (95% CI; 45-66%) and 59% (95%CI; 46 69%), respectively, for the high-risk group, and 75% (95% CI; 68-81%) and 85% (95%CI; 79-90%), respectively, for the non-high-risk group. The DFS and OS HR for high-risk compared to the non-high-risk was 2.0 (95% CI: 1.3 – 3.1, p=0.001) and 3.2 (95% CI: 1.9 – 5.3, p<0.001), respectively. Conclusion: TROG 05.01 patients with ENE and nodal size >22mm were identified as a high-risk subgroup with an inferior DFS. This group could potentially benefit from further adjuvant treatment intensification following surgery and post operative radiation therapy with or without concurrent chemotherapy.

Keywords: cutaneous squamous cell carcinoma, skin, PORT

References: 1.

Porceddu SV, Bressel M, Poulsen MG, Stoneley A, Veness MJ, Kenny LM, et al. Postoperative Concurrent Chemoradiotherapy Versus Postoperative Radiotherapy in High-Risk Cutaneous Squamous Cell Carcinoma of the Head and Neck: The Randomized Phase III TROG 05.01 Trial. Journal of Clinical Oncology. 2018;36(13):1275-83.

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Mini-Oral A first analysis of a phase 1 dose escalation trial of FLASH radiotherapy in patients with skin metastases from melanoma- (NCT04986696) Rémy Kinj 1 , Luis Schiappacasse 1 , Frédéric Duclos 1 , Marine Hebeisen 1 , Wendy Jeanneret-Sozzi 1 , Stéphane Viguet Carrin 2 , Julie Chenal 2 , Patrik Goncalves Jorge 3 , Walter Reiner Geyer 3 , Gian Guyer 3 , Claude Bailat 3 , Francois Bochud 3 , Fernanda Herrera 1 , Olivier Gaide 4 , Raphaël Moeckli 3 , Jean Bourhis 1 1 Department of Oncology, Radio-Oncology Service, Lausanne University Hospital, University of Lausanne, Lausanne, Switzerland. 2 Department of Oncology, Center for Experimental Therapeutics, Lausanne University Hospital, University of Lausanne, Lausanne, Switzerland. 3 Institute of Radiation Physics, Lausanne University Hospital, University of Lausanne, Lausanne, Switzerland. 4 Service of Dermatology, Lausanne University Hospital, University of Lausanne, Lausanne, Switzerland