Abstract
Thyroid nodules with indeterminate fine-needle aspiration cytology (FNA) represent a major challenge in clinical practice. We conducted a systematic review and meta-analysis evaluating the ability of hybrid imaging using fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) to appropriately select these nodules for surgery. PubMed, CENTRAL, Scopus, and Web of Science were searched until July 2019. Original articles reporting data on the performance of 18F-FDG PET/CT in thyroid nodules with indeterminate FNA were included. Summary operating points including 95% confidence interval values (95% CI) were estimated using a random-effects model. Out of 786 retrieved papers, eight studies evaluating 104 malignant and 327 benign thyroid nodules were included. The pooled positive and negative likelihood ratios (LR+ and LR-) and diagnostic odds ratio (DOR) of 18F-FDG PET/CT were 1.7 (95% CI: 1.4–2.0), 0.4 (95% CI: 0.2–0.7), and 3.5 (95% CI: 1.7–7.1), respectively. No heterogeneity was found for LR+ and DOR. In patients with thyroid nodules with indeterminate FNA, 18F-FDG PET/CT has a moderate ability to correctly discriminate malignant from benign lesions and could represent a reliable option to reduce unnecessary diagnostic surgeries. However, further studies using standardized criteria for interpretation are needed to confirm the reproducibility of these findings.
Highlights
IntroductionSeveral steps have been introduced to stratify the risk of malignancy and reduce the number of unnecessary surgical operations
After removal of 113 duplicates, 673 articles were analyzed for title and abstract; 634 records were excluded
We found a low risk of bias: in most studies consecutive patients with thyroid nodules with indeterminate fine-needle aspiration cytology (FNA) were included in a specific period; 18F-FDG PET/CT was evaluated before the final diagnosis or, in retrospective studies, researchers were blinded to final diagnosis [36,38]
Summary
Several steps have been introduced to stratify the risk of malignancy and reduce the number of unnecessary surgical operations. These include a detailed clinical evaluation, laboratory assessment including thyroid stimulating hormone (TSH) measurement, US and fine-needle aspiration cytology (FNA) [2,3]. Cytological classification systems have been developed to improve the communication between cytopathologists and clinicians, and proved to significantly increase the proportion of malignant nodules among resected ones [4]. Four- to six-tiered reporting systems have been developed by different societies and institutions, including the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), the Italian Consensus for the Classification and Reporting of Thyroid Cytology (ICCRTC) and the Reporting of Thyroid Cytology Specimens of the Royal College of Pathologists included in the British Thyroid Association Guidelines for the Management of Thyroid Cancer (BTA) [5,6,7,8,9]
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