ESTRO 2025 - Abstract Book

S3795

Physics - Radiomics, functional and biological imaging and outcome prediction

ESTRO 2025

The risk of occult disease in the ipsilateral LNL III (top panel figure 2) is predicted to be around 2% for early T category cN0 (based on CT) patients. It rises to about 3% for either advanced tumors or if the upstream LNL II harbors visible metastases. Only in case of both does the risk reach 5%, indicating an elective irradiation. In contralateral LNL II, the risk for occult disease is very low (<1%, bottom panel figure 2) as long as the tumor is lateralized. However, as soon as a midline extension is present, it jumps to around 3%, even for early cN0 patients. Therefore, our model suggests sparing the contralateral side for well lateralized tumors.

Conclusion: This model, originally developed for oropharyngeal SCC, accurately and precisely describes lymphatic spread in OCSCC, leveraging multi-institutional data to deliver personalized risk assessments. By supporting substantially reduced CTV-N volumes, the model may inform future clinical trials on de-escalated radiotherapy. If validated, new guidelines derived from its predictions could lead to reduced toxicity and side-effects, while maintaining current treatment efficacy.

Keywords: head & neck, lymphatic spread, CTV-N definition

References: [1] J. Biau et al., "Selection of lymph node target volumes for definitive head and neck radiation therapy: a 2019 Update", Radiother. Oncol., vol. 134, pp. 1-9, May 2019, doi: 10.1016/j.radonc.2019.01.018. [2] R. Ludwig, B. Pouymayou, P. Balermpas, and J. Unkelbach, "A hidden Markov model for lymphatic tumor progression in the head and neck", Sci. Rep., vol. 11, no. 1, p. 12261, Jun. 2021, doi: 10.1038/s41598-021-91544-1. [3] R. Ludwig et al., "A dataset on patient-individual lymph node involvement in oropharyngeal squamous cell carcinoma", Data Br., vol. 43, p. 108345, Aug. 2022, doi: 10.1016/j.dib.2022.108345.