(P30) Prospective Outcomes of Xerostomia-Related quality of Life in Oropharyngeal Carcinoma Patients Treated With Proton Therapy

Abstract

Proton therapy plays an important role in the management of head and neck cancer, where the challenging anatomy benefits from dosimetric advantages of protons. The reduction of treatment-related morbidity is significant for oropharyngeal cancer, as increasingly younger, HPV-positive patients with more favorable prognoses are treated. Patient-reported outcome (PRO) instruments such as the MD Anderson Symptom Inventory (MDASI) have described the response profile of symptoms experienced by patients. Focusing on xerostomia-related quality-of-life outcomes in oropharyngeal carcinoma patients, we prospectively explore xerostomia severity during and after proton therapy, as well as patient- and treatment-specific factors influencing xerostomia. We analyzed xerostomia-related quality-of-life in oropharyngeal carcinoma patients receiving proton therapy between May 1, 2012 and December 31, 2016 at the University of Texas MD Anderson Cancer Center. Inclusion criteria were AJCC 7th Edition Stage III/IV, M0 oropharyngeal carcinoma with documented baseline and at least one response at the primary intervals of interest (6 weeks on treatment, 10 week-, 6-month-, 12-month-, and 24-month follow up). Patients with Stage I/II or M1 disease, or lacking a response at primary intervals above were excluded. The Xerostomia-Related Quality-of-Life Scale (XQ) consists of 15 items scored on a 0-5 Likert scale with higher scores corresponding to more severe symptoms. Piecewise linear mixed effects modeling was used to analyze the mean global XQ response from baseline through 2 years. Our database included 112 patients with oropharyngeal carcinoma treated with proton therapy, with 69 patients satisfying the inclusion criteria. The mean global XQ response was 0.24 at baseline, 2.00 at 6 weeks on treatment, and 1.03, 0.97, 0.82, and 0.70 at 10 weeks, 6 months, 1 year, and 2 years post-treatment, respectively. Furthermore, all changes from baseline were significant (p<0.001) at each of the five respective follow-up time points. The peak XQ response occurred at 6 weeks on treatment, with patients reporting significant improvement by 10 weeks post-treatment. The mean global XQ response after 2 years remained significantly greater than at baseline (n=69); however, less than half of patients contributed information at 2 years (n=26). Similar trends were observed for individual sub-domain scores. Univariate analyses demonstrated significant associations between XQ score and time (p<0.0001 for each time interval) and baseline score (p<0.0001). There were no significant associations between XQ score and age at diagnosis (p=0.223), gender (p=0.659), receipt of chemotherapy (p=0.751), smoking history (p=0.543), or primary disease site (p=0.620). Results from the mixed effects model suggested that baseline global XQ response was significantly associated with global XQ responses measured during treatment and recovery phases. We report prospective outcomes on xerostomia in oropharyngeal cancer patients receiving proton therapy. Patients reported the most severe xerostomia at 6 weeks on treatment with significant recovery by 10 weeks post-treatment; however, xerostomia remained significantly above baseline after 2 years. Xerostomia was associated with time and baseline xerostomia, while no association was detected with age at diagnosis, gender, receipt of chemotherapy, smoking history, or primary disease site. Ongoing studies will establish functional imaging correlates of symptom severity and comparison with conventional photon therapy.