IMRT and Oral Bisphosphonates: Risk Factors for ORN?

Objective: Osteoradionecrosis (ORN) is initiated by trauma to hypovascular and hypocellular bone after head and neck radiotherapy (RT). The objective of this study was to evaluate risk factors for ORN or bone exposure (ORN/BE), including oral bisphosphonate therapy (OBT), a common treatment for osteoporosis. This study also compared the incidence of ORN/BE for conventional RT (CRT) to intensity-modulated RT (IMRT), a newer parotid-sparing method of delivering head and neck RT thought to substantially decrease the incidence of ORN/BE. Methods: The medical and dental records of 641 subjects who received treatment at the University of Florida College of Dentistry and the Shands Cancer Center over a period of twenty years were reviewed. All subjects received head and neck RT (>60 Gy) for cancer of the oral cavity and oropharynx. Factors such as OBT, method of RT delivery (IMRT or CRT) were recorded in the database. Incidence of ORN/BE with each of these risk factors was compared to overall incidence of ORN/BE. Results: Overall incidence of ORN/BE was 24.2% (n=155). The incidence of ORN/BE was 40.9% (n=9) in 22 subjects who had a history of OBT, compared to 23.6% (n=619) in subjects with no known history of OBT (p=0.0756). The incidence of ORN/BE in subjects who were treated with IMRT (n=165) was 20.6% compared to 25.4% in subjects treated with CRT (n=476, p=0.2460). Conclusion: Although not statistically significant, the use of OBT may be an emerging risk factor for ORN/BE in subjects receiving head and neck RT. The incidence of ORN/BE in subjects undergoing IMRT in this study was greater than in previous reports and should be considered a significant risk factor for post-RT dental procedures until proven otherwise. UFCD Student Summer Research Fellowship and NIH/NIDCR Grant T32 DE007200