Indeterminate thyroid nodules. The role of 18F-FDG PET/CT in the “era” of ultrasonography risk stratification systems and new thyroid cytology classifications
- Arnoldo Piccardo, et al
Endocrine volume 69, pages 553–561 (2020
- This paper is using the PET/CT to as a reliable rule out test in Thyroid cancer even when the cytology and and molecular markers are suspicious.
- PET/CT nodules with low SUV were a independent risk factor for benign nodules vs cancer nodules.
- The use of PET/CT in the case of suspicious cytoloy and molecular markers can prevent unnecessary thyroid surgery on benign thyroid nodules.
- This could increase the number of these nodules that can be treated by alternative methods such as Radiofrequency ablation.
- Call me for details of PET/CT use in suspicious thyroid nodules.
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To evaluate the reliability of 18F-FDG PET/CT in distinguishing differentiated thyroid cancers (DTCs) and follicular neoplasms (FNs) from nodular hyperplasias (NH) in thyroid nodules with indeterminate cytology according to the Italian consensus for the classification and reporting of thyroid cytology (ICCRTC). We also tested whether the 18F-FDG PET/CT result was an independent risk factor for DTCs or FNs when sex, age, nodule dimensions, the European Thyroid Imaging and Reporting Data System (EU-TIRADS) and ICCRTC were considered.
We evaluated all patients with thyroid nodules and indeterminate cytology from September 2015 to May 2019; nodules were classified as low risk (TIR3A) and high risk (TIR3B) according to the ICCRTC. Neck ultrasonography features according to EU-TIRADS were re-evaluated and 18F-FDG PET/CT performed. All these patients were surgically treated.
We included 111 patients; 67 nodules were classified as TIR3A and 44 as TIR3B. Overall, we found 27 DTCs, 57 NHs and 27 FNs. Among 73 FDG-negative nodules, we found four low-risk papillary thyroid cancers. All follicular thyroid cancers were identified by 18F-FDG-PET/CT. All TIR3A with low-risk US and negative 18F-FDG-PET/CT were NH. In TIR3A nodules, the sensitivity, specificity, negative and positive predictive values (NPV, PPV) of 18F-FDG PET/CT and EU-TIRADS for DTCs were 77.8%, 41.4%, 92.3%, 17.1% and 66.7%, 56.9%, 91.7%, 19.4%, respectively. In TIR3B nodules, the sensitivity, specificity, NPV and PPV of 18F-FDG PET/CT and EU-TIRADS for DTCs were 88.9%, 38.5%, 83.3%, 50% and 88.2%, 58.3%, 87.5%, 60%, respectively. On multivariate analysis, 18F-FDG-PET/CT (OR 9.04), ICCRTC (O.R. 7.57) and EU-TIRADS (OR 4.41) were all independent risk factors associated to DTCs and FNs.
18F-FDG-PET/CT is a reliable rule-out test for DTC even in thyroid nodules with indeterminate high-risk results. In this subgroup, PPV also tends to be considerable. 18F-FDG-PET/CT results, ICCRTC and EU-TIRADS proved independent risk factors associated to DTCs and FNs.