Prevalence of osteoradionecrosis demonstrated in 18F-FDG PET-CT of post-high-dose-radiotherapy head and neck cancer patients

Results Out of 386 scans, 41 cases demonstrated abnormal increased bony/cartilaginous uptake. Of which 22 were confirmed as residual local osseous involvement of preexisting bony disease, 8 due to disease recurrence at new sites of bone/cartilage, 7 due to benign causes such as dental infection, and 4 due to ORN with no previous local osseous involvement. The incidence of ORN is 1.0% (4/136) of total PET-CT scans and 9.8% (4/41) of increased osseous FDG-uptake. Average occurrence of ORN was 6 months after radiotherapy (range 2 months to 3 years), all received over 60 Gray of radiation dose. Mean-SUVmax of ORN was 6.6, not significantly different from disease recurrence (mean-SUVmax=8.2, P=0.23). Conclusion ORN is a rare complication after high-dose radiotherapy seen in PET-CT (1.0%), but when abnormal increased osseous FDG-uptake is seen within the previous radiotherapy field then ORN should be considered as a differential diagnosis (9.8% of increased osseous uptake). ORN may occur years after treatment and symptoms mimic disease recurrence. There is no significant difference in SUVmax values between ORN and recurrence.