Risk factors for osteoradionecrosis in elderly patients with oral and pharyngeal cancer

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Osteoradionecrosis (ORN) is a serious complication of radiation therapy used in the treatment of squamous cell carcinoma of the oral cavity and pharynx. The incidences reported in clinical series have varied significantly. In this study, we estimate the incidence of ORN and evaluate the variables associated with developing ORN using the SEER-Medicare database. Our analysis was limited to patients who were ≥66 years of age. ORN was identified using Medicare billing records. We estimated the incidence of ORN in the presence of mortality as a competing risk using the cumulative incidence function, controlling for available patient, disease, and treatment characteristics. Risk factors for ORN were identified using the competing risks regression model of Fine and Gray. Two hundred and twenty one of the 5,390 patients developed ORN, representing a crude incidence rate of 4.1 % (95 % CI, 3.6 to 4.7 %). At 1, 2, 5, and 10 years, the incidence of ORN was 1.4, 2.4, 4.1, and 5.9 %. Oral cavity primary (hazard ratio (HR) = 2.67, p < 0.001), multimodality treatment (HR = 1.39, p = 0.04), decreased age (HR = 0.59, p < 0.001), female gender (HR = 0.61, p < 0.001), and stage (HR = 0.43, p = 0.008) were associated with the development of ORN, but only oral cavity primary was not associated with a decreased risk of mortality, showing that mortality is a strong competing risk for ORN. The incidence of ORN continues to increase steadily up to 10 years from the time of diagnosis. Patients with oral cavity primaries are at highest risk in this population. Future research should be directed toward identifying factors that can reduce the incidence of ORN.