The purpose of this study was to analyze the risk factors for osteoradionecrosis (ORN) of the mandible after radiotherapy for treatment of oral or oropharyngeal cancers. Sixty patients with oral or oropharyngeal cancers who had undergone external radiotherapy from January 2011 to December 2016 were retrospectively reviewed. Seven patients(12%) had ORN, and the median time to the development of ORN was 15 months(range, 1-53 months). In the analysis of the whole mandible, univariate analysis revealed that tooth extractions within one month before radiotherapy (p < 0.001), the mean dose of radiotherapy to the mandible (p = 0.04), and the volume of mandible receiving doses of 40Gy (p = 0.02) and 50Gy (p = 0.04) were significant risk factors for ORN. In the analyses of the right and left sides of the mandible, the mean dose of radiotherapy to the mandible and the volume of mandible receiving a dose of 40Gy were significant risk factors(p = 0.04 for each). In the multivariate analysis, tooth extractions in the analysis of the whole mandible was the only significant risk factor for ORN (p < 0.01). Incorporation of both mean dose constraints to the mandible in addition to maximal dose constraints might be needed to reduce the occurrence rate of ORN.

Original languageEnglish
Pages (from-to)57-61
Number of pages5
JournalJapanese Journal of Head and Neck Cancer
Issue number1
Publication statusPublished - 2018


  • Oral cancer
  • Oropharyngeal cancer
  • Osteoradionecrosis
  • Risk factors

ASJC Scopus subject areas

  • Otorhinolaryngology
  • Oncology


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