ESTRO 2025 - Abstract Book

S944

Clinical – Head & neck

ESTRO 2025

review (ICR) & computed quantitative metrics (conformity, homogeneity and gradients indexes) from DICOM RT plans.

Material/Methods: Patient inclusion criteria were PS 0-2, life expectancy ≥6mo, controlled primary, 1-3 PET-confirmed oMet, cumulated PTV≤7cm. Fraction (3 or 5) size & total dose were standardized on oMet size, anatomic location, distance from critical organs & AAPM-based dose constraints. All SABR equipments were allowed provided that they were adequate for intra & extracranial SABR & centers passed the benchmark case credentialing step. ICR was performed retrospectively based on expert-based assessment of indication, prescription, image guidance, organs at risk (OAR) & oMet contours, fulfillment of OAR & tumor dose constraints indicated in protocol. ICR was performed by two radiation oncologists for all patients & blind to patients’ outcomes. Correlations between ICR items & Kaplan Meier estimation with log rank test by type and severity of deviation were performed. Results: Of 69 pts from 11 centers, included from 2016 to 2022, there were 81.2% male of 62.7 yo, PS1-2 52.3% & with significant comorbidities 81.7%, HPV 23.2%, lung-only 82.6%, isolated 58.0% oMets. Median follow-up was 53.7 months; 1y-OS was 63.4 months (95%CI 47.6-84.5) with SABR-alone & 61.7 (95%CI 46.2-82.4) with chemo-SABR. Local failure at SABR-treated oMets occurred in 7 chemo-SABR & 7 SABR-alone patients. The number of oMets (HR 3.36 (95%CI 0.94-12.02, p=0.06) was the sole clinical prognostic factor for survival. By ICR, the number of minor & major deviations of OAR contours & dose, oMet contours & dose, image guidance were similar between trial arms (p>0.162-to-0.999). Compared to patients without deviation, patients with ≥1 minor (N=37) or major (N=7) deviation of oMet dose was associated with poorer survival (median 61, 50 & 27 months, p<0.0001). Compared to no deviation of oMet dose, patients with minor (N=4) & major (N=2) deviation was associated with poorer survival (median 48, 6 & 2 months, p<0.0001). For patients with single oMet, tumor volume (p=0.059), RTOG max homogeneity index (p=0.002) were different between those with major deviations, minor deviations or no deviation. Conclusion: Based on ICR, there was no imbalance of SABR quality between the chemotherapy-and-SABR & SABR-alone arms. The presence of ≥1 major deviation was associated with poorer survival. References: 1: Thariat J, Bosset M, Falcoz A, et al. Survival without Quality of Life Deterioration in the GORTEC 2014-04 “OMET” Randomised Phase 2 Trial in Head and Neck Cancer Patients with Oligometastases using Stereotactic Ablative Radiotherapy (SABR)-alone or chemotherapy SABR. Int J Radiat Biol Phys 2024 (in press). 2: Khalladi N, Dejean C, Bosset M, Pointreau Y, Kinj R, Racadot S, Castelli J, Huguet F, Renard S, Guihard S, Tao Y, Rouvier JM, Johnson A, Bourhis J, Xu Shan S, Thariat et alJ. A priori quality assurance using a benchmark case of the randomized phase 2 GORTEC 2014-14 in oligometastatic head and neck cancer patients. Cancer Radiother. 2021 Dec;25(8):755-762. Keywords: oligometastasis, stereotactic, quality assurance

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Digital Poster Mucosa sparing strategy in Head and neck cancers treated with hypofractionated carbon-ion therapy Ankita Anil Nachankar 1,2 , Joanna Gora 3 , Mansure Schafasand 3,4 , Eugen Hug 1 , Antonio Carlino 3 , Piero Fossati 5,1 1 Radiation Oncology, MedAustron Ion therapy, Wiener Neustadt, Austria. 2 Medical Research and Development, ACMIT Gmbh, Wiener Neustadt, Austria. 3 Medical Physics, MedAustron Ion therapy, Wiener Neustadt, Austria.