Dosimetric Predictors of Acute and 1-Year Functional Oral Intake for Head and Neck Cancer Patients Treated with Radiotherapy

Abstract

<h3>Purpose/Objective(s)</h3> In order to reduce risks of radiation-induced dysphagia after head and neck radiotherapy, a better understanding of the relationship between dose to various swallowing-related organs at risk (SOARs) is necessary. There is limited data regarding the association of 6–12-month functional swallowing outcomes and the dose to SOARs including the pharyngeal constrictor muscle (PC), cricopharyngeus (C), glottic (GL) supraglottic larynx (SGL), and the RTOG-defined Pharynx OAR (POAR). We assessed dosimetric predictors of change in swallowing function from up to 1-year post-RT. <h3>Materials/Methods</h3> We retrospectively reviewed our institutional database of patients treated with head and neck cancer from 2017-2020. Swallowing function was assessed at 1-, 3-, 6-, and 12-months post-treatment using the Functional Oral Intake Scale (FIOS, 1=no oral intake, 7=total oral intake without restrictions). Mean dose, V50, and V60 were abstracted from the treatment planning software for each SOAR. Patients were categorized by whether clinically relevant constraint parameters were met for each SOAR, which were then evaluated for association with FOIS using the Wilcoxon test. <h3>Results</h3> In total, 141 patients with evaluable treatment plans and swallowing outcomes were analyzed. Of the patients included for analysis, 51% had oropharyngeal cancer, 100% received concurrent chemotherapy, and 31% were treated post-operatively. Across all included treatment plans, the median prescribed dose to PTV was 70 Gy (38-70 Gy). Swallowing outcomes at 1-, 3-, 6-, and 12-months post-treatment were available for 132 (94%), 129 (91%), 121 (86%), and 111 (79%) patients, respectively. The median (range) FOIS scores at baseline, 1-, 3, 6-, and 12-months were 7 (5-7), 4 (2-7), 6 (3-7), and 7 (6-7). For each swallowing structure the mean (Gy) doses (listed as median (IQR)) were: 57.7 (49.0-64.3) for PC, 47.3 (38.7-51.4) for C, 38.9 (33.6-43.4) for GL, 47.4 (38.8-52.2) for SGL, and 53.2 (45.4-59.5) for POAR. The V50 (%) for each SOAR was: 77.5% (52.6-93.5) for PC, 23.3% (5.1-59.8) for C, 0.2% (0-5.1) for GL, 36.4% (19.5-48.5) for SGL, and 67.3% (42.8-86.6) for POAR. The V60 (%) for each SOAR was: 47.5% (23.0-75.5) for PC, 0.5% (0-8.6) for C, 0% (0-0) for GL, 21.4% (4.2-34.5) for SGL, and 32.2% (8.3-55.7) for POAR. On dosimetric analysis, PC mean≤50Gy, POAR mean≤45Gy, and POAR V50<33% were associated with increased FOIS at 1- and 3-months (p<0.05). POAR V60<15% and SGL mean<=40Gy was associated with FOIS at 1-mo (p<0.05). No evaluated factors were associated with 6- or 12-month FOIS. <h3>Conclusion</h3> Lower doses of radiation to pharyngeal constrictor, RTOG-defined pharynx, and supraglottic larynx are associated with improved swallowing function in patients with head and neck cancer. Radiation treatment plans should be optimized to reduce dose to these structures in order to improve acute swallowing outcomes. A larger sample size is needed to better evaluate the impact of radiation dose to these structures on long term swallowing outcomes.