ESTRO 2021 Abstract Book

S606

ESTRO 2021

Conclusion This study showed that sarcopenia in HNSCC patients undergoing RT was an independent prognostic factor for the development of physician-rated acute dysphagia grade≥3 and late dysphagia grade≥2 and grade≥3, which might be explained by its impact on the swallowing muscles. However, sarcopenia did not improve the performance of NTCP-models RT-induced other evaluated acute toxicities. PD-0775 External validation of photon-derived NTCP models for acute toxicity in head and neck proton therapy L. Van den Bosch 1 , A. van der Schaaf 1 , H.P. van der Laan 1 , J.G. van den Hoek 1 , T.W. Meijer 1 , E. Oldehinkel 1 , R.J. Steenbakkers 1 , J.A. Langendijk 1 1 University Medical Centre Groningen, Radiation Oncology, Groningen, The Netherlands