title: Osteoradionecrosis of the mandibula in patients treated with different fractionations.
abstract: OBJECTIVE
  The incidence of osteonecrosis of the mandibula (ON) after irradiation using modern three-dimensional planning as well as hyperfractionation or moderately accelerated irradiation has been evaluated and compared with the incidence of the preceding period.
  
  
  METHODS
  The records of 268 head and neck cancer patients irradiated between January 1, 1980 and December 31, 1998 with a dose to the mandibula of at least 60 Gy were retrospectively analyzed. All patients had CT-based treatment planning, computerized dose calculation with isodose charts also in several off-axis planes, and regular verification films.
  
  
  RESULTS
  The long-term cumulative incidence of ON needing mandibular resection was as follows: after conventional fractionation 6.2% (between 60 and 66.6 Gy target dose) or 20.1% (between > 66.6 and 72 Gy); after hyperfractionated irradiation with a target dose between 72 and 78.8 Gy 6.6%; after concomitant boost irradiation according to the MDA/Houston regime with a dose between 63.9 and 70.5 Gy: no case; after 6 x 2 Gy/week or 7 x 1.8 Gy/week and a total target dose between 66 and 72 Gy approximately 17% or higher (small patient number).
  
  
  CONCLUSIONS
  Comparison of the incidence of ON during the period between 1980 and 1990 with the following period between 1990 and 1998 shows a decrease in risk to a value of approximately 5% using modern three-dimensional techniques as well as hyperfractionation or moderately accelerated fractionation.
authors.affiliation: Department of Radiation Oncology, University Hospital Zurich, Switzerland. Gabriela.Studer@usz.ch
authors.forename: Gabriela
authors.initials: G
authors.lastname: Studer
authors.forename: Klaus W
authors.initials: KW
authors.lastname: Grätz
authors.forename: Christoph
authors.initials: C
authors.lastname: Glanzmann
mesh_terms: D016009:Chi-Square Distribution; D003729:Dental Care; D019583:Dose Fractionation, Radiation; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D015994:Incidence; D008334:Mandible / Q000528:radiation effects; D008336:Mandibular Diseases / Q000453:epidemiology / Q000209:etiology*; D010025:Osteoradionecrosis / Q000453:epidemiology / Q000209:etiology*; D016016:Proportional Hazards Models; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D013997:Time Factors; D014057:Tomography, X-Ray Computed