Clinical Use of A Priori Knowledge of Organ-At-Risk Sparing During Radiation Therapy Treatment for Oropharyngeal Cancer: Dosimetric and Patient Reported Outcome Improvements

Purpose: This study aimed to prospectively assess dosimetric and clinical effects of treatment planners having a priori knowledge of the maximum achievable dose sparing for organs at risk (OARs) for patients with oropharynx cancer receiving intensity modulated radiation therapy (RT). Methods and Materials: We examined patients with oropharynx cancer who were treated in prospective clinical trials between February 2012 and April 2019 at our institution. A tool generating estimates of maximum achievable dose sparing for OARs (feasibility dose-volume histogram [FDVH]) was used clinically starting July 2016. Patients were divided into 2 cohorts: Before (ie, baseline) and after (ie, FDVH-guided) FDVH. Doses received by various OARs were compared with those estimated to be achievable per FDVH, and that difference was defined as the excess of feasible dose (EFD). Patient-reported outcome (PRO) questionnaires were completed at 3, 6, and 12 months after treatment. The baseline and FDVH-guided cohorts were compared in terms of EFD, plan quality metrics, and post-RT PRO assessments. Results: A total of 139 patients were included in the analysis (60 in the baseline cohort, 79 in the FDVH-guided cohort). The FDVH-guided cohort had lower EFD to the contralateral parotid by 4.1 Gy, the ipsilateral parotid by 10.6 Gy, the larynx by 4.3 Gy, the oral cavity by 1.5 Gy, and the contralateral submandibular gland by 0.4 Gy. Plan quality metrics were similar between the cohorts. Less variation of EFD was seen in the FDVH-guided cohort for the parotid glands and contralateral submandibular gland (P < .05). The average post-RT PROs were better in the FVHD cohort versus baseline (particularly at the 6-month timepoint for dry mouth frequency, sticky saliva, meal enjoyment, severity of pain, and Eating Assessment Tool 10 composite [swallowing]; P < .05). Conclusions: Use of FDVH was associated with improved and less variable OAR sparing for clinically delivered plans. FDVH-guided patients had improved PROs compared with baseline with a variety of outcomes significantly improved at 6 months after treatment. (C) 2021 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.