Detection of extranodal spread in head and neck cancer with [18F]FDG PET and MRI: improved accuracy?

Aim. Preoperative detection of extranodal spread (ENS) in head and neck cancer can have important consequences for patient management. The aim of this study was to determine whether 18-fluorodeoxyglucose positron emission tomography ([18F]FDG PET) or a combination with Magnetic Resonance Imaging (Mm) could more accurately predict ENS, especially with the near availability of fully integrated [18F]FDG PET/MRI scanners.

Methods. In retrospective cohort design a total of twelve patients, with 18 lymphnode metastases were studied with [18F]FDG PET and MM. Presence of ENS was scored on MRI, and [18F]FDG PET images using a SUV max cut-off point of 12. Histopathology results were used as reference standard. Sensitivity, specificity and accuracy were calculated.

Results. The sensitivity, specificity and accuracy of [18F]FDG PET for ENS reached 70%,100% and 83%, respectively. The mean SUVmax of ENS positive lymphnodes was 13.6 versus 8.7 for lymphnode metastases without ENS (P=0.03). The sensitivity, specificity and accuracy of MM for ENS were 70%, 100% and 83%, respectively. When the [18F]FDG PET and MM findings were combined sensitivity, specificity and accuracy were 80%, 100% and 89%, respectively. Thus, accuracy increased from 83% to 89%.

Conclusion. When there is no ENS or doubt of ENS on MM, [18F]FDG PET seems to have additional value since it improves sensitivity and resolves uncertainty in case of high FDG uptake. This benefit needs to be confirmed prospectively in a larger cohort.