Dedicated neck ¹⁸F‐FDG PET/CT: An additional tool for risk assessment in thyroid nodules at ultrasound intermediate risk

Abstract

Summary Background Several ultrasound (US) risk stratification systems have been proposed for the assessment of thyroid nodules, and their performance was shown as good. However, the rate of nodules assessed at intermediate risk is not negligible and whether they should be submitted or not to further examination is still under debate. The present study aimed to evaluate the reliability of 18F‐FDG PET/CT in stratifying the risk of malignancy in these lesions. Methods Two institutions participated to this retrospective study in which a dedicated 18F‐FDG PET/CT was proposed to patients having a thyroid nodule with US assessment of EU‐TIRADS 4 or 5. 18F‐FDG PET/CT did not influence the diagnostic and therapeutic decision. Histology was the gold standard for all patients. Results Ninety‐three patients were included for the study with 48 EU‐TIRADS 4 and 45 EU‐TIRADS 5 nodules. Of these, 26 underwent thyroidectomy following FNAC suspicious for or consistent with malignancy, 38 for inconclusive cytology, 27 because of large goitre and 2 for high‐risk lesion at US. At histology, 35 carcinomas and 58 benign lesions were found. Cancer prevalence was 16.7% in EU‐TIRADS 4 and 60% in EU‐TIRADS 5. Overall, 18F‐FDG PET/CT was positive in 33/35 cancers (94.5% sensitivity) and negative in 31/58 benign lesions (53.4% specificity). When considering only EU‐TIRADS 4, 18F‐FDG PET/CT was positive in 7/8 cancers and negative in 20/40 benign lesions; among these, there were 36 cases with FNAC indication according to dimensional cut‐off (ie >1.5 cm), and 18F‐FDG PET/CT showed 85.7% sensitivity and 41.4% specificity. Conclusions 18F‐FDG PET/CT may have a role in stratifying the cancer risk of thyroid nodules with an intermediate ultrasound assessment. More specifically, thyroid lesions classified as EU‐TIRADS 4 and with no 18F‐FDG uptake could be ruled out from further examination, similar to other anamnestic and clinical suspicious factors of patients. Further prospective and cost‐effectiveness studies are needed.

Quantitative classification and radiomics of [18F]FDG-PET/CT in indeterminate thyroid nodules

“…With a limited 40% specificity, visual [ 18 F]FDG-PET/CT assessment increased the post-test risk of malignancy but appeared unable to fully risk-stratify the approximately two-thirds visually [ 18 F]FDG-positive nodules [4]. These results validated the findings from previously published, smaller, non-randomised studies [5][6][7][8][9][10][11][12].…”

Histopathological Verification of the Diagnostic Performance of the EU-TIRADS Classification of Thyroid Nodules—Results of a Multicenter Study Performed in a Previously Iodine-Deficient Region

“…In a recent paper by Trimboli et al, the authors evaluated the potential role of 18F-Fluorodeoxyglucose(FDG)PET/CT in the risk stratification of thyroid nodules suspected of malignancy [31]. A PET/CT scan might increase the negative predictive value of the EU-TIRADS scale and allow a 41% reduction in the number of biopsies, while only one case of thyroid cancer would be missed.…”

The New Era of TIRADSs to Stratify the Risk of Malignancy of Thyroid Nodules: Strengths, Weaknesses and Pitfalls

“…In a report on 80 nodules, no significant differences were observed in elasticity score or strain ratio between benign and malignant nodules [54]. 18F-FDG PET/CT could be a more useful tool to discriminate intermediate risk nodules [55]. 18F-FDG PET/CT showed 85.7% sensitivity and 41.4% specificity.…”