Dosimetric Risk Factors for Patient-Reported Dysphagia Among Head and Neck Cancer Patients Receiving Definitive Radiation Therapy

Abstract

Acute dysphagia during head and neck cancer (HNC) chemoradiation (CRT) is a significant complication that may lead to patient morbidity, RT interruption and potentially late dysphagia due to disuse atrophy of the swallow muscles. As patient-reported outcomes (PRO) offer the potential for more accurate assessments, we sought to pilot evaluate the dosimetric relationships that affected the maximum score of the validated Sydney Swallow Questionnaire (SSQ) that is weekly administered to our HNC patients to gain insights into reducing the risk of CRT-acute dysphagia. HNC patients treated with intensity-modulated-CRT from April 2015 to July 2017 in our institution were evaluated. The SSQ is a 17-question validated patient-reported assessment of physiologic swallow and was prospectively administered using electronic tablets at consult, weekly on-the-treatment visits (OTV), and in follow up visits. The study was limited to patients who had not undergone prior irradiation to the HN region, surgery, or had no pre-treatment swallow difficulty (baseline SSQ total score >234) and with no missing SSQ assessments. Our primary outcome was the highest OTV SSQ total score. Patient demographic and clinical data included age, gender, race, HPV status, smoking, chemotherapy, tumor location. Dose data included radiation dose at 10% increments (i.e. D0, D10, . D100) for the ipsilateral and contralateral parotid and submandibular glands (relative to the location of the primary tumor), superior constrictor (SC) muscle, and cricopharyngeal muscle. Univariate and stepwise multivariate linear regressions were conducted. We identified 58 patients with a mean age at diagnosis of 60 years old. Mean baseline and highest OTV SSQ scores were 68 (7-194) and 529 (36 – 1605) respectively. The time at which patients reported the highest SSQ was observed: 17% at week 2, 7% at week 3, 12% at week 4, 21% at week 5, 28% at week 6 and 16% at week 7. Multivariate analysis identified the contralateral parotid gland D40 and the SC muscle D100. Each 1 Gy increase in the contralateral parotid glands and SC muscle was associated with an increase in 9.64 (95%CI: [3.75 - 15.51], p<0.01) and 13.90 SSQ total score (95% CI: [5.87 - 21.92], p<0.01), respectively. Our pilot results suggest that the dose to the contralateral parotid gland and SC muscle may play a role in the development of acute CRT-related PRO dysphagia. Our findings underscore the value of OTV SSQ assessments and how acute PRO dysphagia may be affected by parotid function, which may not be captured by physician-graded swallowing function. Ongoing efforts by our group include the development of a comprehensive atlas of swallow-related structures that can be deformably registered along with continued OTV SSQ evaluations. This work offers the promise of reducing the severity of CRT-related PRO dysphagia.