Exclusion of Malignancy in Thyroid Nodules with Indeterminate Fine‐Needle Aspiration Cytology After Negative ¹⁸F‐Fluorodeoxyglucose Positron Emission Tomography: Interim Analysis

Abstract

Background In all, 20% of fine‐needle aspiration (FNA) biopsies of thyroid nodules have an indeterminate diagnosis; of these, 80% are found to be benign after thyroidectomy. Some previous reports indicate that positron emission tomography (PET) with 18F‐fluorodeoxyglucose (FDG) imaging may predict malignancy status. We now report results on the first 51 patients in the largest prospective study of FDG‐PET in patients with an indeterminate thyroid nodule FNA. Methods Eligible patients had a dominant thyroid nodule that was palpable or ≥1 cm in greatest dimension as seen by ultrasonography, and indeterminate histology of the FNA biopsy specimen. Participants underwent preoperative neck FDG‐PET alone or FDG‐PET with computed tomography (FDG‐PET/CT). Images were evaluated qualitatively and semiquantitatively using the maximum standardized uptake value (SUVmax). Final diagnosis was determined by histopathologic analysis after thyroidectomy. Descriptive statistical analysis was performed. Results A total of 51 patients underwent preoperative FDG‐PET or FDG‐PET/CT. Studies without focally increased uptake localized to the lesion were considered negative. For all lesions (10 malignant, 41 benign), the sensitivity, specificity, positive‐predictive value (PPV), and negative‐predictive value (NPV) were 80%, 61%, 33%, and 93%, respectively. Postoperatively, two malignant and six benign lesions were found to be <1 cm by pathology examination; one lesion was not measured. When these lesions were excluded, the sensitivity, specificity, PPV, and NPV were 100%, 59%, 36%, and 100%, respectively. Conclusions Based on these preliminary data, FDG‐PET may have a role in excluding malignancy in thyroid nodules with an indeterminate FNA biopsy. This finding justifies ongoing accrual to our target population of 125 participants.

The role of 18F-fluorodeoxyglucose positron emission tomography in differentiated thyroid cancer before surgery

“…Seven previous studies have evaluated the usefulness of FDG PET for the differentiation of indeterminate nodules of the thyroid, yielding conflicting results (Kresnik et al 2003, de Geus-Oei et al 2006, Kim et al 2007, Sebastianes et al 2007, Hales et al 2008, Traugott et al 2010, Deandreis et al 2012. The sensitivity of FDG PET was 57-100%, depending on the characteristics of the patient population.…”

The Role of 18F-Fluorodeoxyglucose Positron Emission Tomography in Thyroid Neoplasms

“…At present, there is no alternative algorithm for more conservative management of patients with indeterminate FNAC. Convectional USG, CT, and magnetic resonance imaging (MRI) have previously been shown to be of some value, but FDG-PET has yet to be assessed in a large prospective study [25]. Table 3 shows a comparison of series examining the utility of FDG-PET in detecting malignancy in a thyroid nodule with indeterminate FNAC findings [25,29,[37][38][39][40][41].…”

“…However, because most of these reported series were retrospective in design and the patient selection was not formally standardized, there is a need for a large, well-designed prospective study. Recently, Traugott et al [25] reported the results of 51 patients with indeterminate FNAC findings in an interim analysis of their prospective trial, which began in 2004. Their data suggested that FDG-PET was an accurate diagnostic modality for identifying malignancy in thyroid nodules Ն1 cm in diameter and with indeterminate FNAC results, with 100% sensitivity and NPV.…”

“…In one recent study, among 15 cases of suspected follicular variant of PTC, only two cases (13.3%) had unanimous agreement among six expert pathologists [44]. Given these concerns, the role of FDG-PET in evaluating thyroid nodules with indeterminate FNAC findings remains uncertain, but the interim results in one of the possibly largest prospective trials on FDG-PET in cytologically indeterminate nodules look promising [25]. Hopefully, this prospective trial, which is due to be completed in the next few years, will provide us with more information.…”

Noninvasive In Vivo Imaging and Biologic Characterization of Thyroid Tumors by ImmunoPET Targeting of Galectin-3

“…18 F-FDG PET has been used but its sensitivity and specificity are questioned, although a cancer diagnosis is generally ruled out in the presence of negative result (4)(5)(6). PET imaging of a thyroid cancer-associated marker would be preferable.…”