Delineation of the “Oropharyngeal Mucosa” and Limiting its Dose in Head and Neck Cancer Patients Spares the Oropharynx Without Compromising Target Coverage

Abstract

Objectives Radiation-induced oropharyngeal injury is a dose-limiting toxicity in head and neck cancer patients. Delineation of the “oropharyngeal mucosa” and limiting its dose to spare the oropharynx was investigated. Methods In this retrospective study, computed tomography imaging from eight patients with previously untreated head and neck cancer was employed. An adaptive contouring brush within the planning software Monaco was used to create an air cavity within the oropharynx, and then the air cavity was expanded uniformly 2 mm to create the “oropharyngeal mucosa”. Three plans were independently generated for each patient: Plan1: dose constraint was applied for the oropharynx; Plan2: dose constraints were applied for the oropharynx and the “oropharyngeal mucosa”; Plan3: dose constraint was applied for the “oropharyngeal mucosa”. T-tests were used to compare the dosimetry variables. Results All plans had adequate target coverage and there were no statistical differences among plans. The mean dose, D30%, D45%, D50%, D85%, D90%, D95%, D100%, V25 Gy, V30 Gy, V35 Gy, V40 Gy, and V45 Gy of the oropharynx and “oropharyngeal mucosa” in Plan1 were significantly higher than those in Plan2 and Plan3. There were no significant differences between Plan2 and Plan3. There were no significant differences in the dosimetric parameters of any other organs at risk. Conclusion Delineation of the “oropharyngeal mucosa” and limiting its dose should be an easy and effective method to spare the oropharynx.