Abstract
PURPOSE: To determine dosimetric parameters associated with osteoradionecrosis (ORN) in oropharyngeal cancer (OPC) patients in the IMRT era. MATERIAL AND METHODS: Subsequent to institutional review board approval, we identified ORN in OPC patients treated with IMRT from 2002 to 2013. 1:2 case-control matching was implemented. Mandibular dose-volume histograms (DVH) were extracted. Dosimetric parameters were compared using non-parametric stats. Recursive partitioning analysis (RPA) was done to identify DVH correlates of ORN. RESULTS: 68 ORN cases and 131 controls were matched. Median follow-up was 41months and median time to development of ORN was 16months. Mandibular mean dose was significantly higher in the ORN cohort (48.1 vs 43.6Gy, p<0.0001). However, the maximum dose was not statistically different. DVH bins from V35 to V73 were all significantly higher in the ORN cohort compared with controls (p<0.0006). Two DVH parameters were identified in RPA analysis, V43 and V58. The majority (81%) of ORN cases were observed with both V44≥42% and V58≥25%. CONCLUSIONS: Our data demonstrate that a wide range of DVH parameters in the intermediate and high beam path were all significantly higher in ORN patients. Mandibular V44<42% and V58<25% represent reasonable DVH constraints for IMRT plan acceptability, when tumor coverage is not compromised.