Incidence of, and risk factors for, mandibular osteoradionecrosis in patients with oral cavity and oropharynx cancers.

OBJECTIVES: To evaluate the incidence of, and risk factors associated with, mandibular osteoradionecrosis (MORN) following radiation therapy (RT) for oral cavity and oropharyngeal cancers.

MATERIALS AND METHODS: Patient and treatment records of 252 consecutive patients with oral cavity or oropharynx cancers treated with RT by a single radiation oncologist at a high volume academic institution from August 2009 to December 2015 were retrospectively reviewed. A Cox regression model was used to assess factors associated with the development of MORN. RT dosimetry was compared between patients with MORN and a matched cohort of patients without MORN.

RESULTS: MORN developed in 14 patients (5.5%), occurring 3-40 (median 8) months post-RT. Factors associated with MORN on univariable analysis included primary diagnosis of oral cavity vs oropharynx cancer (hazard ratio [HR]: 3.0, p=0.04), smoking at the time of RT (HR: 3.1, p=0.04), mandibular invasion of the primary (HR: 3.7, p=0.04), pre-RT tooth extraction (HR: 4.52, p=0.01), and treatment with 3D-conformal RT vs intensity-modulated RT (HR: 5.1, p=0.003). On multivariable analysis, pre-RT tooth extractions and RT technique remained significant. A dosimetric comparison between patients with and without MORN showed no significant differences.

CONCLUSIONS AND RELEVANCE: The incidence of MORN is low in the modern era at a high volume academic center. Modifiable risk factors including pre-RT tooth extractions, smoking, and RT technique are associated with MORN, and the risk should be minimized with appropriate dental evaluation and treatment, smoking cessation efforts, and the use of intensity-modulated RT.