Risk Factors of Patient-Reported Xerostomia Among Oropharyngeal Cancer Survivors Treated with Definitive Radiotherapy

PURPOSE/OBJECTIVE(S) Xerostomia is a common sequela of radiation therapy (RT) and chemoradiotherapy (CRT). Head and neck cancer treatment can contribute to salivary glands injury with diminished salivary production and changes in consistency, volume, and pH of saliva. Previous studies examining xerostomia have investigated RT regimens, dosimetric predictors, and quality of life (QoL) associations but few have identified clinicodemographic risk factors for xerostomia and quantified their associations among oropharyngeal carcinoma (OPC) survivors. The objective of this study was to identify risk factors for xerostomia among long-term OPC survivors. MATERIALS/METHODS This was a cross-sectional study conducted at a comprehensive cancer center. Study participants included disease-free, adult OPC survivors who completed curative definitive radiotherapy treatment between January 2000 and December 2013, and responded to a survey administered from September 2015 to July 2016. This study included 881 OPC survivors with a median survival duration at time of survey of 7 years (range, 1-16 years) of which self-reported xerostomia scores were available for 853 participants. The primary outcome variable was patient-reported xerostomia measured using the MD Anderson Symptom Inventory Head and Neck Cancer Module. Clinicodemographic risk factors for moderate to severe xerostomia were identified using multivariable logistic regression. RESULTS Of 853 OPC survivors who responded to the xerostomia question, 337 (39.5%) reported moderate to severe xerostomia. Multivariable logistic regression identified current smoking at time of survey (OR:2.57, 95% CI: 1.20-5.53, P = 0.016) as a risk factor for moderate to severe xerostomia and concurrent cetuximab chemotherapy (OR:0.63; 95% CI: 0.41-0.97, P = 0.038) as a protective factor. Additionally, female sex (OR:1.81, 95% CI: 1.21-2.71, P = 0.004) and less than high school education (OR:1.68, 95% CI: 1.15-2.45, P = 0.008) were risk factors for moderate to severe xerostomia and bilateral intensity modulated radiotherapy (IMRT) combined with proton therapy (OR:0.34, 95% CI: 1.16-0.73, P = 0.005) and ipsilateral IMRT (OR:0.18, 95% CI: 0.07-0.46, P < 0.001) were protective. CONCLUSION In this large xerostomia study, about 4 out of 10 OPC survivors reported moderate to severe xerostomia over long-term follow-up. Continued smoking after cancer diagnosis, sex, and education were identified as important risk factors of moderate to severe xerostomia and concurrent cetuximab therapy and more modern RT regimens had a protective association. Sustained smoking post-diagnosis is a modifiable risk factor which can be addressed with continued smoking cessation efforts. Lastly, these results can inform future research and targeted patient-centered interventions to monitor and manage RT-associated xerostomia and preserve QoL among OPC patients.