Abstract
IMPORTANCE: Xerostomia and reduced mouth opening are negatively associated with quality of life after radiation therapy (RT) for head and neck cancer. Studies comparing objective measures of function with patient-reported outcomes (PROs) have not revealed a clear association. OBJECTIVE: To determine how much of the variation in PROs is explained by objective measures of salivary gland and oral cavity functions (salivary flow and maximal interincisal opening). DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional study at a single academic cancer center evaluated 112 patients who underwent RT for head and neck cancer between January 2016 and March 2021. Measurements of pre-RT and post-RT saliva and a complete PROs scale within 6 months of the post-RT measurement were analyzed using pairwise associations. INTERVENTIONS: Three independently scored PRO scales from the validated FACE-Q Head and Neck Cancer Module were evaluated: eating and drinking, eating distress, and salivation. Three objective measures were analyzed: maximal interincisal opening, stimulated salivary flow, and unstimulated salivary flow. MAIN OUTCOMES AND MEASURES: Univariable linear regression models were performed for each PRO against each objective measure, and coefficients of determination (R2) and 95% CIs were reported. RESULTS: The patient cohort comprised 86 men (77%). Median age was 61 years (IQR, 53-68 years), 89 patients (80%) were White, and 61 patients (54%) were current or former smokers. Unstimulated saliva accounted for only a small portion of variation on the salivation scale (R2 = 14.0%). The remaining associations were even smaller (R2 = 5.0%-10.0%). No upper 95% CI bound included an R2 of 30%, suggesting that objective measurements do not explain a high level of the variation in PROs. CONCLUSIONS AND RELEVANCE: In this cross-sectional study, objective measurements of salivary flow and mouth opening explained only a small fraction of variation in PROs. These findings suggest that factors other than objective function, including patient adaptation, are the dominant influence on PROs in this population. Patient-reported outcomes should be integrated into head and neck cancer clinical care and research. Additional research is required to evaluate which clinicopathological factors influence PROs for salivation, eating and drinking, and eating distress.