Comprehensive Assessment of the Relationship Between Oral Cavity Dosimetry and Patient Reported Xerostomia and Dysgeusia

Abstract

Xerostomia and dysgeusia are two common and severe complications for patients undergoing head and neck chemoradiotherapy (CRT). Literature suggests a relationship between mean oral cavity (OC) doses and worsening xerostomia and dysgeusia. However, limited data exists identifying which substructures of the oral cavity are most related to patient reported outcomes (PROs) or how oral cavity dosimetry should be prioritized in relationship to other salivary glands during planning. We hypothesized that only certain substructures of the OC will be related to patient reported xerostomia and dysgeusia and that OC dose will be less impactful than contralateral major salivary gland dose for patient reported xerostomia and dysgeusia.184 and 177 prospectively enrolled patients for de-escalated CRT for HPV-positive oropharyngeal cancer submitted PROs at 6 and 12 months, respectively using PRO-CTCAE 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 OAR dosimetry to patient reported xerostomia and dysgeusia at 6 and 12 months. Multivariate ordinal logistic regression models were determined using forward/backward AIC minimization to minimize the number of predictive variables.Mean dose to the contralateral parotid (P = 0.04), OC (P = 0.04), and baseline patient reported xerostomia (P = 0.009) were significantly associated with xerostomia severity at 6 months. Only baseline xerostomia (P = 0.02) and mean dose to the contralateral submandibular gland (P = 0.0001) 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 = 0.009). Upon examining substructures, the mean dose to the floor of mouth was implicated for the dose relationship to 6-month xerostomia (P = 0.04) and the oral tongue was found to be implicated for the relationship for 12-month dysgeusia (P = 0.04).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 impact of OC dose relative to other salivary structures for xerostomia appeared to depend on time post-CRT (comparable to contralateral parotid at 6 months and not significant at 12 months).