Osteoradionecrosis and radiation dose to the mandible in patients with oropharyngeal cancer.
OBJECTIVE
To determine the association between radiation doses delivered to the mandible and the occurrence of osteoradionecrosis (ORN).


METHODS
We reviewed the records of 402 oropharyngeal cancer patients with stage T1 or T2 disease treated with definitive radiation between January 2000 and October 2008 for the occurrence of ORN. Demographic and treatment variables were compared between patients with ORN and those without. To examine the dosimetric relationship further, a nested case-control comparison was performed. One to 2 ORN-free patients were selected to match each ORN patient by age, sex, radiation type, treatment year, and cancer subsite. Detailed radiation treatment plans for the ORN cases and matched controls were reviewed. Mann-Whitney test and conditional logistic regression were used to compare relative volumes of the mandible exposed to doses ranging from 10 Gy-60 Gy in 10-Gy increments.


RESULTS
In 30 patients (7.5%), ORN developed during a median follow-up time of 31 months, including 6 patients with grade 4 ORN that required major surgery. The median time to develop ORN was 8 months (range, 0-71 months). Detailed radiation treatment plans were available for 25 of the 30 ORN patients and 40 matched ORN-free patients. In the matched case-control analysis, there was a statistically significant difference between the volumes of mandible in the 2 groups receiving doses between 50 Gy (V50) and 60 Gy (V60). The most notable difference was seen at V50, with a P value of .02 in the multivariate model after adjustment for the matching variables and dental status (dentate or with extraction).


CONCLUSIONS
V50 and V60 saw the most significant differences between the ORN group and the comparison group. Minimizing the percent mandibular volume exposed to 50 Gy may reduce ORN risk.
Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
Chiaojung Jillian
CJ
Tsai
Theresa M
TM
Hofstede
Erich M
EM
Sturgis
Adam S
AS
Garden
Mary E
ME
Lindberg
Qingyi
Q
Wei
Susan L
SL
Tucker
Lei
L
Dong
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D008334:Mandible / Q000528:radiation effects*; D008336:Mandibular Diseases / Q000453:epidemiology* / Q000209:etiology; D008875:Middle Aged; D009959:Oropharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D010025:Osteoradionecrosis / Q000453:epidemiology* / Q000209:etiology; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D018709:Statistics, Nonparametric