Radiation Dose to Swallowing Muscles and Post-Radiotherapy Laryngeal Penetration or Aspiration in Head and Neck Squamous Cell Carcinoma

Background/Objectives: Radiation-induced dysphagia can cause life-threatening complications including aspiration pneumonia. Consequently, studies have attempted to limit the radiation dose to the swallowing muscles to prevent radiation-induced dysphagia. However, data identifying the specific swallowing muscles associated with post-radiation dysphagia are lacking. Therefore, this case–control study aimed to identify the swallowing muscles whose radiotherapy-related damage is likely to cause radiation-induced dysphagia. Methods: This retrospective study included 53 patients with head and neck cancer who received definitive radiotherapy and underwent post-radiotherapy swallowing function evaluation using videofluoroscopy or fiberoptic endoscopic evaluation of swallowing at least 3 months post-radiotherapy. Twenty-two patients with a Penetration-Aspiration Scale score ≥ 3 were defined as having laryngeal penetration or aspiration. Twenty-two controls matched for age and tumor site were selected using propensity score matching. The primary exposure variable was radiation dose to the swallowing muscles, including the floor of the mouth, thyrohyoid, posterior digastric/stylohyoid, longitudinal pharynx, hyoglossus, styloglossus, genioglossus, and intrinsic tongue muscles. A LASSO regression model was used to select the most predictive dosimetric parameter. Results: The percentage of genioglossus muscle receiving a radiation dose ≥70 Gy (GGS V70) was the only dosimetric variable predictive of radiation-induced dysphagia. After adjusting for the clinical variables, GGS V70 demonstrated a significant association with post-radiotherapy laryngeal penetration or aspiration (p = 0.003), with an adjusted odds ratio of 1.06 for each increasing radiation dose unit of GGS V70. Conclusions: The genioglossus muscle might be associated with radiation-induced dysphagia and, therefore, should be further investigated in prospective studies.