ESTRO 2026 Congress Report | Physics track I Proffered Papers Session

Authors: Sven Meijer, Markus Wendling, Patricia Doornaert, Frank Hoebers, Bas Kreike, Marije Vergeer, Ellen Zwijnenburg, Tim Dijkema, Erik van der Bijl, Johannes Kaanders, Sven van den Bosch

The randomised controlled UPGRADE-RT trial demonstrated the safety of reduced-dose elective neck irradiation in patients with larynx and pharynx cancers and was therefore adopted as standard of care in the Netherlands. It was also demonstrated that patients treated with a reduced elective dose (43 Gy) required tube feeding significantly less often in the first 90 days after starting their radiotherapy course compared to controls (50 Gy). Stratified for tumour site, this reduction in tube feeding dependency was only observed in the subgroup of hypopharynx and larynx cancer patients, but not in patients with oropharynx cancer. Interestingly, the mean dose to the pharyngeal mucosa was similar in both subgroups, and the difference in mucosa mean dose between standard- and reduced-dose arms was also similar within the subgroups. Therefore, we could not explain the difference in tube feeding incidence between subgroups by the mean dose to the pharyngeal mucosa. We hypothesised that the spatial distribution of the dose in the mucosa might explain the discrepancy.

In order to assess the dose distribution in the pharyngeal mucosa, we acquired dose surface maps (DSMs) of the pharynx, which project the surface dose of a structure onto a 2D grid. DSMs have proven their use in toxicity prediction in the rectum, bladder, heart, and oesophagus, but have not been used for the pharynx before. DSMs of the pharynx were spatially aligned across patients using anatomical landmarks and information about the laterality of the gross tumour volume. Absolute dose difference maps were used to assess group differences. Pixel-wise statistical analysis identified regions where the dose difference between groups was statistically significant.

Maps of dose difference between patients with and without tube feeding demonstrated that patients requiring tube feeding had significantly higher dose to the mucosa of the epiglottis and the pharyngeal wall at the level of the epiglottis. For the subgroup of larynx and hypopharynx cancer patients, a significantly lower dose was observed in this same mucosal area (i.e., the epiglottis and the pharyngeal wall at this level) in patients treated with a reduced dose compared to a standard dose. For oropharyngeal cancer patients, no significant dose differences in this mucosal area were observed between those patients who were treated with a reduced dose compared to the standard dose. These findings indicate that there is heterogeneity in the association between radiation dose to the different mucosal subregions of the pharynx and the risk of requiring tube feeding. A higher dose to the mucosal subregion of the epiglottis and the pharyngeal wall at this level was observed in patients requiring tube feeding. Incorporating the peri-epiglottic mucosal region as an organ-at-risk for radiation treatment dose optimisation may therefore contribute to reducing tube feeding dependency during treatment.

Sven Meijer
Medical physics resident
Department of Radiation Oncology, Radboudumc, the Netherlands
Email: sven.meijer@radboudumc.nl
LinkedIn: www.linkedin.com/in/sven-meijer-01