Dynamic Whole-Body FDG PET/CT as a Novel Tool for Predicting Malignancy in Primary ENT Tumors and Cervical Lymphadenopathy

Background: Dynamic whole-body (D-WB) FDG PET/CT is a novel technique that enables the direct reconstruction of multiparametric images representing the FDG metabolic uptake rate (MRFDG) and "free" FDG (DVFDG). Applying complementary parameters with distinct characteristics compared to static SUV images, the aims of this study are as follows: 1) to determine the threshold values of SUV, MRFDG, and DVFDG for malignant and benign lesions; 2) to compare the specificity of MRFDG and DVFDG images with static SUVbw images; 3) to assess whether any of the dynamic imaging parameters correlate more significantly with malignancy or non-malignancy in the examined lesions based on the measured values obtained from D-WB FDG PET/CT. Results: Patlak PET parameters (MRFDG, DVFDG) combined with mean SUVbw achieved the highest accuracy of 0.82 (F1-score = 0.90) for malignancy detection. Classification accuracy in tumors was 0.86 (F1 = 0.92), lymph nodes reached 0.81 (F1 = 0.89). Relative contribution analysis showed that DVFDG accounted for up to 65 % of classification weight. The ROC analysis demonstrated AUC values above 0.8 for all models, with optimal thresholds achieving sensitivities around 0.85 and specificities up to 0.93. Thresholds for malignancy detection were for mean values: SUVbw>5.8 g/mL, MRFDG>0.05 µmol/mL/min, DVFDG> 68 %; for maximal values: SUVbw> 8.7 g/mL, MRFDG> 0.11 µmol/mL/min, DVFDG> 202 %. Conclusions: The D-WB [¹⁸F]FDG PET/CT images in this study highlight the potential for improved differentiation between malignant and benign lesions compared to conventional SUVbw imaging in patients with locally advanced head and neck cancers presenting with cervical lymphadenopathy and carcinoma of unknown primary (CUP). This observation may be particularly relevant in common diagnostic dilemmas, especially in distinguishing residual or recurrent tumors from post-radiotherapy changes. Further validation in larger cohorts with histopathological confirmation is warranted.