Osteoradionecrosis in Pediatric Patients Treated with Proton Therapy for Head and Neck Malignancies.

Abstract

Purpose: Osteoradionecrosis (ORN) is a feared complication after head and neck radiation, but the incidence and radiotherapy risk factors for ORN in children are unknown. In this retrospective analysis of a prospectively collected dataset, we evaluated the incidence and factors associated with development of ORN in children treated with proton therapy for head and neck malignancies.

Methods and materials: We reviewed records from patients treated at a single institution between December 2006 and February 2020 including demographic data, tumor, and treatment details, ORN occurrence, and dosimetry. Differences between groups and the predictive value of dosimetric characteristics were assessed with Mann-Whitney U tests, simple linear regression, and Fisher's exact tests.

Results: We identified 117 pediatric patients treated with proton therapy for head and neck malignancies. The most common histology was rhabdomyosarcoma (46%), and the most common involved sites were the parameningeal sites (44%) and the orbit (32%). The majority received passive scatter (n=81, 69%) and the remainder IMPT (n=36, 31%). Only two (1.7%) developed ORN. Age, mean mandible doses, and radiation technique (3D vs. IMPT) did not predict for ORN. Patients with ORN had higher doses to the mandible than those without ORN, including Dmax (p=0.029), D0.5cc (p=0.039), D1cc (p=0.036), V60Gy (p=0.01), V55Gy (p=0.02), and V50Gy (p=0.048). The most significant predictors of ORN by linear regression were mandible V50Gy (r²=0.053, p=0.01), V55Gy (r²=0.094, p<0.01), and V60Gy (r²=0.17, p<0.001). Dosimetric characteristics associated with development of ORN included Dmax>60Gy (p=0.037), D0.5cc>60Gy (p=0.031), D1cc>59Gy (p=0.028), and V55Gy>2cc (p=0.034).

Conclusions: ORN is uncommon in pediatric patients treated with proton therapy for head and neck malignancies, occurring in 1.7% of patients in our cohort. Patients with mandible Dmax>60Gy, D0.5cc>60Gy, D1cc>59Gy, and V55Gy>2cc are at greatest risk for ORN.