Evaluation of physiologic and abnormal glucose uptake in palatine tonsils: differential diagnostics with sequential dual-time-point 2-deoxy-2-[18F]FDG PET/CT.

BACKGROUND: The aim of this article was to evaluate the usefulness of sequential dual-time-point 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography (DTP [18F]FDG PET/CT) in distinguishing physiologic, inflammatory and malignant palatine tonsils as difficult to differentiate in the oncological practice.

METHODS: A total of 90 patients before the treatment underwent sequential DTP [18F]FDG PET/CT examinations. We analyzed 104 structures in 90 patients: 31 physiologic tonsils, 28 histopathologically confirmed inflammatory tonsils of non-specified origin, 31 histopathologically confirmed palatine tonsils cancer and 14 non-malignant contralateral tonsils in patients with histopathologically confirmed unilateral palatine tonsil malignancy. Patients underwent sequential [18F]FDG PET/CT examinations at 60 and 90 minutes post-injection of the [18F]FDG. We analyzed the SUVmax and SUVmean values at 60 and 90 minutes post-injection changes over time and the Retention Index (RI-SUVmax). To find the predictive SUV value and the RI cut-off between physiology, inflammatory and malignancy, we used the ROC analysis.

RESULTS: The average SUVmax values at 60 and 90minutes post-injection within physiologic palatine tonsils were 1.36±0.26 and 1.31±0.26, respectively, P>0.05. The average SUVmax values at 60 and 90 minutes post-injection within inflammatory and malignant tonsils were 3.74±1.45, 3.80±1.47 (P>0.05) and 5.19±2.19, 5.81±2.50 (P<0.05), respectively. The RI-SUVmax fluctuation over time were 5±28% within physiologic, -4±11% within contralateral non-malignant tonsils in patients with one tonsil involved, 2±11% within inflammatory and 13±13% within malignant tonsils.

CONCLUSIONS: The sequential dual-time-point [18F]FDG PET/CT examinations may increase the sensitivity and the specificity of the PET/CT method in differential palatine tonsils diagnosis.