ESTRO 2025 - Abstract Book

S1083

Clinical – Head & neck

ESTRO 2025

actionable thresholds to inform clinical decision-making and enhance preventive strategies. Further analyses with larger cohorts are essential to validate the results and refine the model for broader clinical application.

Keywords: ORN, HNC, Predictive Risk Assessment

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Poster Discussion ITHACA-CHRONOS: Impact of Radiotherapy Timing on Toxicity and Outcomes in Head and Neck Cancer Patients mariangela massaccesi 1 , Silvia Longo 1 , Francesco Pastore 1 , Ciro Mazzarella 1 , Antonella Martino 1 , Stefania Manfrida 1 , Calogero Casà 2 , Francesco Ciardo 1 , Francesco Miccichè 2 , Giuseppe Ferdinando Colloca 1 , Luca Tagliaferri 1 , Vincenzo Frascino 1 , Maria Antonietta Gambacorta 1 1 Dipartimento Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy. 2 Dipartimento Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fatebenefratelli Isola Tiberina-Gemelli Isola, Rome, Italy Purpose/Objective: Head and neck squamous cell carcinoma (SCC) patients often face significant toxicities from radiotherapy (RT) or chemoradiotherapy (CRT), which can impact survival and treatment adherence. Emerging evidence suggests that timing RT according to circadian rhythms may reduce treatment-related toxicities. The ITHACA-CHRONOS study evaluates the effect of RT session timing on toxicity, recurrence, and survival outcomes in SCC patients. Material/Methods: This study included 463 SCC patients treated with RT or CRT from January 2013 to August 2024. Patients were divided into two groups: early treatment (8:00–10:00 AM) and late treatment (after 10:00 AM). The primary outcomes measured were severe (Grade 3+) acute toxicities and overall survival (OS), based on CTCAE v5.0 criteria. Results: Acute toxicity rates were significantly higher in the late treatment group (n=334). Grade 3 toxicities occurred in 38.9% of patients in the late group, compared to 17.6% in the early group (p=0.012). Grade 4 toxicities were observed in 26.3% of the late group versus 7.7% in the early group (p=0.008). Kaplan-Meier survival analysis revealed no statistically significant difference in survival between the two groups (log-rank p=0.0607), though some trends were noted. Conclusion: Although survival differences between groups were not statistically significant, earlier RT timing was associated with a marked reduction in severe toxicities in SCC patients. These findings suggest that circadian-aligned RT scheduling could offer clinical benefits, highlighting the need for further research to optimize treatment strategies and improve patient outcomes.

Keywords: circadian rhythms, head and neck, radiotherapy

References: Ali YF, Hong Z, Liu NA, Zhou G. Clock in radiation oncology clinics: cost-free modality to alleviate treatment-related toxicity. Cancer Biol Ther. 2022 Dec 31;23(1):201-210. doi: 10.1080/15384047.2022.2041953. PMID: 35263235; PMCID: PMC8920191. Yao J, He C, Zhao W, Hu N, Long D. Circadian clock and cell cycle: Cancer and chronotherapy. Acta Histochem. 2021 Dec;123(8):151816. doi: 10.1016/j.acthis.2021.151816. Epub 2021 Nov 17. PMID: 34800857.