Radiation dose to the floor of mouth muscles predicts swallowing complications following chemoradiation in oropharyngeal squamous cell carcinoma

Objectives While radiation dose to the larynx and pharyngeal constrictors has been the focus of swallowing complications, the suprahyoid muscles, or floor of mouth (FoM) muscles, are critical for hyoid and laryngeal elevation and effective bolus diversion, preventing penetration and aspiration. We hypothesize that radiation dose to these muscles may be important in the development of dysphagia. Materials and methods We studied 46 patients with OPSCC treated with CRT and who underwent baseline swallowing evaluations and post-treatment videofluoroscopic swallowing studies (VFSS) from 2007 to 2010. Patients with abnormal penetration aspiration scores (PAS > 2) served as the study population and patients with normal PAS scores (≤2) served as the control cohort. Three suprahyoid muscles and two extrinsic tongue muscles were individually delineated and collectively referred to as the FoM muscles. Radiation dose-volume relationships for these muscles were calculated. Univariate logistic regression analysis was used to determine parameters of significance between patients with normal or abnormal PAS scores. A multivariate regression analysis was subsequently performed to isolate the most statistically critical structures associated with abnormal PAS. Results Univariate analysis resulted in significance/borderline significance of multiple structures associated with abnormal PAS following irradiation. However, when a multivariate model was applied, only the mean dose to the floor of mouth and minimum dose to the geniohyoid were associated with post-radiation abnormal PAS. Conclusions The dose and volume delivered to the collective FoM muscles may be associated with an increased risk of laryngeal penetration/aspiration to a greater degree than previously recognized organs at risk.