Intensity-modulated radiotherapy of head and neck cancer aiming to reduce dysphagia: early dose-effect relationships for the swallowing structures.

PURPOSE: To present initial results of a clinical trial of intensity-modulated radiotherapy (IMRT) aiming to spare the swallowing structures whose dysfunction after chemoradiation is a likely cause of dysphagia and aspiration, without compromising target doses. METHODS AND MATERIALS: This was a prospective, longitudinal study of 36 patients with Stage III-IV oropharyngeal (31) or nasopharyngeal (5) cancer. Definitive chemo-IMRT spared salivary glands and swallowing structures: pharyngeal constrictors (PC), glottic and supraglottic larynx (GSL), and esophagus. Lateral but not medial retropharyngeal nodes were considered at risk. Dysphagia endpoints included objective swallowing dysfunction (videofluoroscopy), and both patient-reported and observer-rated scores. Correlations between doses and changes in these endpoints from pre-therapy to 3 months after therapy were assessed.
RESULTS: Significant correlations were observed between videofluoroscopy-based aspirations and the mean doses to the PC and GSL, as well as the partial volumes of these structures receiving 50-65 Gy; the highest correlations were associated with doses to the superior PC (p = 0.005). All patients with aspirations received mean PC doses >60 Gy or PC V(65) >50%, and GSL V(50) >50%. Reduced laryngeal elevation and epiglottic inversion were correlated with mean PC and GSL doses (p < 0.01). All 3 patients with strictures had PC V(70) >50%. Worsening patient-reported liquid swallowing was correlated with mean PC (p = 0.05) and esophageal (p = 0.02) doses. Only mean PC doses were correlated with worsening patient-reported solid swallowing (p = 0.04) and observer-rated swallowing scores (p = 0.04).
CONCLUSIONS: These dose-volume-effect relationships provide initial IMRT optimization goals and motivate further efforts to reduce swallowing structures doses to reduce dysphagia and aspiration.