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

## TL;DR

This study finds that high radiation doses to the genioglossus muscle are linked to swallowing problems and aspiration after head and neck cancer radiotherapy.

## Contribution

The study identifies genioglossus muscle radiation dose as a novel predictor of post-radiotherapy dysphagia and aspiration.

## Key findings

- The percentage of genioglossus muscle volume receiving ≥70 Gy radiation (GGS V70) is predictive of radiation-induced dysphagia.
- Each unit increase in GGS V70 is associated with a 1.06-fold increased odds of post-radiotherapy laryngeal penetration or aspiration.
- Genioglossus muscle damage is a significant factor in radiation-induced swallowing complications.

## Abstract

Radiation-induced dysphagia is a common adverse effect of radiotherapy in patients with head and neck cancer and may lead to life-threatening complications, including aspiration pneumonia. This case–control study aimed to identify swallowing muscles whose radiation-related injury is associated with the development of radiation-induced dysphagia. In our cohort of 44 patients, the percentage of genioglossus muscle volume receiving a radiation dose ≥ 70 Gy (GGS V70) emerged as the dosimetric parameter predictive of radiation-induced dysphagia.

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.