Author: Matthew D Blackledge, Christopher M. Nutting, Anju Mohanan Kaimal, Justine Tyler, Konstantinos Zormpas-Petridis 👨🔬
Affiliation: Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Institute of Cancer Research, The Royal Marsden NHS Foundation Trust, The Institute of Cancer Research 🌍
Purpose: Swallowing dysfunction (dysphagia) is a common side effect of radiotherapy for oropharyngeal cancer, significantly affecting patient's quality of life. This study aims to investigate the relationship between high-dose exposure to pharyngeal constrictor muscles (PCM) and dysphagia by analysing dose-surface maps (DSMs) and their association with the MD Anderson Dysphagia Inventory (MDADI) scores.
Methods: Data from 112 patients treated for oropharyngeal cancer were analysed, with 94 complete MDADI assessments at 12 months post-radiotherapy. DSMs were generated by projecting 3D dose distributions onto 2D surfaces of the PCM and dividing them into a 3x3 dose grid (nine anatomical zones denoted DSM0 to DSM8). A Bayesian logistic regression model was used to identify baseline DSM and clinical predictors that stratified patients into the lower and upper 50th percentiles of 12-month MDADI scores. DSM heatmaps and posterior distributions of the coefficients were visualized for interpretation.
Results: Among all DSM zones, DSM7 which represented the central region of the superior PCM, showed a significantly negative coefficient with MDADI scores, indicating that high-dose exposure in this region significantly increases the likelihood of dysphagia. The DSM7 showed a statistically significant coefficient of -1.5 (94% high density interval = -2.5 to -0.37) suggesting its role in swallowing dysfunction.
Conclusion: This study highlights the importance of anatomically analysing DSMs to identify high-risk regions within the PCM. Sparing DSM7 during radiotherapy planning could mitigate the risk of dysphagia and improve patient outcomes. These findings provide a basis for adaptive radiotherapy strategies that minimize high-dose exposure to critical PCM regions.