Evaluation of decentralised model-based selection of head and neck cancer patients for a proton treatment study. DAHANCA 35

Introduction: Proton treatment can potentially spare patients with H&N cancer for substantial treatmentrelated toxicities. The current study investigated the reproducibility of a decentralised model-based selection of patients for a proton treatment study when the selection plans were compared to the clinical treatment plans performed at the proton centre. Methods: Sixty-three patients were selected for proton treatment in the six Danish Head and Neck Cancer (DAHANCA) centres. The patients were selected based on normal tissue complication probability (NTCP) estimated from local photon and proton treatment plans, which showed a ANTCP greater than 5%-point for either grade 2 + dysphagia or grade 2 + xerostomia at six months. The selection plans were compared to the clinical treatment plans performed at the proton centre. Results: Of the 63 patients, 49 and 25 were selected based on an estimated benefit in risk of dysphagia and xerostomia, respectively. Eleven patients had a potential gain in both toxicities. The mean ANTCP changed from the local selection plan comparison to the clinical comparison from 6.9 to 5.3 %-points (p = 0.01) and 7.3 to 4.9 %-points (p = 0.03) for dysphagia and xerostomia, respectively. Volume differences in both CTV and OAR could add to the loss in ANTCP. 61 of the 63 clinical plans had a positive ANTCP, and 38 had a ANTCP of 5%-points for at least one of the two endpoints. Conclusion: A local treatment plan comparison can be used to select candidates for proton treatment. The local comparative proton plan overestimates the potential benefit of the clinical proton plan. Continuous quality assurance of the delineation procedures and planning is crucial in the subsequent randomised clinical trial setting. (c) 2023 The Author(s). Published by Elsevier B.V. Radiotherapy and Oncology 190 (2024) 109812 This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).