Evaluation of the Prevalence and Risk Factors for Osteoradionecrosis of the Jaw in Patients Treated with Intensity-modulated Radiation Therapy

This study aimed to estimate the prevalence and determine the risk factors for the development of osteoradionecrosis （ORN） of the jaw after intensity-modulated radiation therapy （IMRT）. The cases of 114 patients who achieved complete remission after undergoing IMRT for head and neck cancer between 2011 and 2017 were retrospectively reviewed. The treatment involved IMRT with simultaneous integrated boost. The maximum dose delivered to the mandible and the mean dose delivered to the maxillae were kept below 70Gy and 35Gy, respectively. Age, sex, disease stage, the intent of radiation therapy, the maximum dose delivered to the jaw, whether the patient was dentulous or edentulous, the presence/absence of chemotherapy, diabetes mellitus, and smoking history were evaluated as risk factors for ORN. ORN was observed in 3 maxillae and 4 mandibles, and a total of 7 （6.1%） patients developed ORN during a median follow-up period of 15 months （6-28 months）. The maximum dose delivered to the jaw （70Gy） was significantly related to the development of ORN of the jaw. No other significant factors were identified. As ORN was observed in 3maxillae, we should consider dose constraints for both the mandible and maxillae to prevent ORN of the jaw