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

Aim: Our 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.
Methods: Sixteen 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 (2h 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.
Results: Histopathological 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).
Conclusion: This 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.
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