Background: Patients with head and neck cancer (HNC) treated with radiation therapy (RT) are at risk for jaw osteoradionecrosis (ORN) which is largely characterized by presence of exposed necrotic bone. This report describes the incidence and clinical course of and risk factors for exposed intraoral bone in the multicenter Observational Study of Dental Outcomes in Head and Neck Cancer Patients (OraRad) cohort. Methods: Participants were evaluated before RT and at 6, 12, 18 and 24 months after RT. Exposed bone was characterized by location, sequestrum formation, and other associated features. Radiation dose to the affected area was determined and history of treatment for exposed bone was recorded.

Results: The study enrolled 572 participants; 35 (6.1%) were diagnosed with incident exposed bone at 6 (47% of reports), 12 (24%), 18 (20%), and 24 (8%) months, with 60% being sequestrum and 7 cases (20%) persisting for >6 months. The average maximum RT dose to the affected area of exposed bone was 5456 cGy (SD 1768); the most frequent associated primary RT sites were the oropharynx (42.9%) and oral cavity (31.4%); 76% of episodes occurred in the mandible. ORN diagnosis was confirmed in 18 participants, an incidence rate of 3.1% (18/572). Risk factors included pre-RT extractions (p=0.008), higher RT dose (p=0.039) and tobacco use (p=0.048).

Conclusions: The two-year incidence of exposed bone in the OraRad cohort was 6.1%; the incidence of confirmed ORN was 3.1%. Exposed bone after RT for HNC is relatively uncommon and in most cases a short-term, not recurring or persistent complication. Precis for use in the Table of Contents The two-year incidence of exposed bone in the OraRad cohort was 6.1% and the incidence of confirmed cases of jaw osteoradionecrosis was 3.3%. Exposed bone after radiation therapy for head and neck cancer is relatively uncommon and in most cases a short-term, not recurring or persistent complication.