Risk stratification of incidental 18F-Fluorodeoxyglucose-avid thyroid nodules based on six societies’ ultrasound risk stratification systems
Chae Young Shin, Gangneung-si / Korea, Republic of
Author Block: C. Y. Shin1, D. G. Na1, H. S. Lee1, H. S. Ahn2; 1Gangneung-si/KR, 2Seoul/KRPurpose: This study was aimed to determine the risk of malignancy in thyroid incidentalomas (TIs) detected on 18F-FDG PET/CT using the six societies’ ultrasound (US)-risk stratification systems (RSSs) and to evaluate the diagnostic value of the SUVmax in PET-TIs.Methods or Background: This study included 215 consecutive patients with 236 TIs detected by focal thyroid uptake on 18F-FDG PET/CT. The final diagnoses were obtained by US-guided biopsy or thyroidectomy. The malignancy risk of all TIs were assessed according to the six US-RSSs including ACR-, Chinese (C)-, European (EU)-, and Korean-TIRADS.Results or Findings: The overall malignancy rate of TIs was 47% and the malignancy risk of TIs was stratified by all US-RSSs (all, P<- 001). The observed malignancy risks of high-suspicion TIs were higher than the estimated malignancy risks only in ACR-, C-, and EU-TIRADSs (P≤0.035). The malignancy risks of intermediate-suspicion TIs were higher than the estimated malignancy risks in all US-RSSs (24.8-48.2%, P≤0.002). The malignancy risks of low-suspicion TIs were higher than the estimated malignancy risk only in the C- and EU-TIRADS (35% and 10%, respectively, P≤0.01). The SUVmax of malignant tumours was higher than that of benign nodules (4.7 versus 2.8, P<0.001) and the AUC for malignancy was 0.708. The SUVmax of high-grade malignancy was higher than that of low-grade malignancy (7.4 versus 4.0, P=0.002).
Conclusion: The malignancy risk of intermediate-suspicion TIs was increased in all US-RSSs, whereas the malignancy risks of high- and low-suspicion TIs was increased in only some RSSs. The biopsy size thresholds for intermediate suspicion TIs should be lowered in all US-RSSs. The SUVmax showed a fair diagnostic performance for malignancy in PET-TIs and the SUVmax needs to be considered in biopsies.Limitations: No limitation were identified.Funding for this study: No funding was received for this study.Has your study been approved by an ethics committee? Not applicableEthics committee - additional information: This study is under the review of the ethics committee (number: 2023-09-007).