Dual-phase F-18 FDG PET–CT in staging and lymphoscintigraphy for detection of sentinel lymph nodes in oral cavity cancers

AimOur objective was to evaluate the diagnostic role of dual-phase fluor-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography–computed tomography (PET–CT) and planar lymphoscintigraphy in patients with oral cavity cancer (OCC). We also investigated the combined impact of F-18 FDG PET–CT and sentinel lymph node biopsy (SLNB) in decision making for patients with OCC.MethodsSixteen patients (4 female, 12 male; age range, 29–81 years) were included in this prospective study. F-18 FDG PET–CT [1 (early) and 2 h (delayed) after injection] and planar lymphoscintigraphy (2 h before the surgery) were performed for all the patients before surgery. The sensitivity, specificity, and negative and positive predictive values in F-18 FDG PET–CT for the early and the delayed scans and tumor/liver uptake (T/L) in the lymph nodes were calculated. Receiver operating characteristic curves were obtained for standardized uptake value (SUV)max and T/L.ResultsHistopathological evaluations revealed that 5 patients had metastatic lymph nodes (pN +) whereas 11 patients had benign lymph nodes (pN −). Out of 43 lymph nodes visualized as cN(+) in F-18 FDG PET–CT, 14 were pathologically positive for malignancy, whereas 29 were pathologically benign. There was no statistical difference between the N(+) and N(−) patients in terms of age, depth of primary tumor, and the number of mitoses. However, there was a significant difference between the N(+) and N(−) patients (P= .011) in terms of early and delayed F-18 FDG uptake of primary tumors. There was a statistically significant difference in the value of SUVmax between the early and the delayed scans for the malignant lymph nodes (P= .00).ConclusionThis study indicates that F-18 FDG PET–CT is a reliable method for the correct evaluation of primary tumor and N staging in OCCs. Delayed phase of F-18 FDG imaging may increase primary lesion detectability due to higher FDG uptake in primary tumors compared to the early phase of imaging. F-18 FDG PET–CT might demonstrate skip metastasis in lymph nodes which can be missed with SLNB. Although SUV values increased in the delayed phase of F-18 PET–CT imaging in detecting lymph node metastases, the specificity and positive predictive value did not increase.