Endocrine Abstracts

Backgrounds: With increasing use of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG PET) in the clinical field, thyroid nodules are one of the common incidental findings. It is reported that about one third of these nodules are proven to be malignant nodule. In this study, efficacy of quantitative PET indexes in predicting the cytopathology of thyroid nodules was evaluated.

Methods: A total of 338 patients with thyroid nodules detected on FDG PET from 2019 to 2024 were retrospectively enrolled. The nodules were further examined with fine needle aspiration (FNA). Quantitative PET indexes such as maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), were measured in the thyroid nodule. Their efficacies in predicting the cytopathologic nature of the nodule by FNA were evaluated along with other clinical variables such as age, gender, size, thyroid function test values.

Results: SUVmax and TLG of thyroid nodule were statistically significant in predicting cytopathology based on Bethesda scoring system (P value of 0.001 and 0.005, respectively). SUVmax and TLG tended to increase as the category escalated, with highest value in the malignant category (Bethesda VI). SUVmax was able to discriminate the group with higher risk of malignancy (Bethesda IV, V, VI) from lower risk group (Bethesda II, III) with optimal cutoff value set as 4.8 (sensitivity 70.5, specificity 64.2, AUC 0.718). Other variables were not statistically significant in predicting malignant groups.

Conclusion: Quantitative indexes of FDG PET are well associated with Bethesda scoring system in thyroid nodules. Measuring SUVmax of thyroid nodule on FDG PET can aid in predicting the cytopathology and thus guiding the optimal treatment for the patient.