Impact of Oral Cavity Dosimetry on Patient Reported Xerostomia and Dysgeusia in the Setting of Deintensified Chemoradiotherapy

PURPOSE: To determine the relationship between mean oral cavity (OC) dose (treated as a singular organ at risk) to patient reported xerostomia and dysgeusia. In addition, we will examine the relationship between oral cavity substructure doses to patient reported xerostomia and dysgeusia. All patients were treated in the setting of deintensification (60 Gy). METHODS AND MATERIALS: In the study, 184 and 177 prospectively enrolled patients for de-escalated chemoradiotherapy (CRT) for human papillomavirus (HPV)-positive oropharyngeal cancer submitted PROs at 6 and 12 months, respectively using Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events questionnaire. Patient's OC consisting of the following substructures were segmented: oral tongue, base of tongue, floor of mouth, hard and soft palate, cheek mucosa, and upper and lower lip mucosa. Ordinal logistic regression (no/mild vs moderate vs severe/very severe symptoms) was used to compare organs at risk dosimetry to patient reported xerostomia and dysgeusia at 6 and 12 months. Multivariate ordinal logistic regression models were generated. RESULTS: Mean dose to the contralateral parotid (P = .04), OC (P = .04), and baseline patient reported xerostomia (P = .009) were significantly associated with xerostomia severity at 6 months. Only baseline xerostomia (P = .02) and mean dose to the contralateral submandibular gland (P = .0001) were significantly associated with xerostomia severity at 12 months. The only significant factor related to dysgeusia at either time point was mean dose to the OC at 12 months (P = .009). On examining substructures, the mean dose to the floor of mouth was implicated for the dose relationship to 6-month xerostomia (P = .04), and the oral tongue was found to be implicated for the relationship for 12-month dysgeusia (P = .04). CONCLUSIONS: The mean dose to the OC was found to relate to xerostomia symptoms at 6 months post-CRT and dysgeusia symptoms at 12 months post-CRT. The mean dose to the floor of mouth and oral tongue appeared to drive this relationship for xerostomia and dysgeusia symptoms, respectively. This work suggests the floor of mouth and oral tongue should be prioritized during planning over the rest of the OC. The effect of OC dose relative to other salivary structures for xerostomia appeared to depend on time post-CRT.