Ultrasound stratification of the FDG-avid thyroid nodule

Sonographic risk stratification of FDG-avid thyroid nodules using the Thyroid Imaging Reporting and Data System

INTRODUCTION

The increasing usage of positron emission tomography/computed tomography (PET/CT) for detection and monitoring of malignancy has led to an increase in incidental detection of thyroid nodules. Nodules that demonstrate increased avidity for 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) have been shown to carry a high incidence of malignancy and warrant further investigation. At present, there has been limited research on the risk stratification of FDG-avid thyroid incidentalomas. Thus, this study aims to evaluate the efficacy of the ACR TIRADS classification in the risk stratification of such nodules.

METHODS

Data were collected retrospectively for FDG-avid thyroid incidentalomas over a 10-year period. Nodules were characterised using the TIRADS classification and, subsequently, underwent fine-needle aspirate cytology. Cytological findings were classified using the Bethesda reporting system. Non-diagnostic samples (Bethesda class I) were excluded. The remaining samples were divided into two groups: benign (Bethesda class II) or suspicious for malignancy/malignant (Bethesda class III or above).

RESULTS

Thirty-six percent of low-risk nodules and 45% of high-risk nodules were malignant, respectively (P = 0.516). The sensitivity and specificity of TIRADS for detection of malignant nodules were 56% and 54%, respectively. There were no malignant TIRADS 1 or 2 nodules. The absence of any suspicious sonographic features had a 1.0 negative predictive value.

CONCLUSIONS

FDG-avid nodules classified as TIRADS 1 or 2 or have no suspicious ultrasound features have a 0% incidence of malignancy and thus may not require further assessment with fine-needle aspirate cytology (FNA) when detected incidentally. FDG-avid nodules that are TIRADS 3 or above should undergo FNA regardless of size due to the high risk of malignancy and poor sensitivity of the TIRADS classification system.

Incidentally detected 18 F-FDG PET-CT-avid thyroid nodules in patients with advanced malignancy: long-term oncological outcomes from a single-centre retrospective cohort

OBJECTIVES

In this retrospective study, we assessed the clinical outcomes of patients with a primary malignancy who had incidentally detected thyroid avidity on their staging 18 F-fluorodeoxyglucose PET-computed tomography ( 18 F-FDG PET-CT) examinations.

METHODS

A focused retrospective search was made using a Radiology Information System to identify only patients with positive thyroid nodules on their 18 F-FDG PET-CT imaging between January 2012 and December 2017. Patient demographics, principal oncological diagnosis, and stage were recorded. The sonographic appearances of thyroid nodules, number of fine needle aspiration (FNA) attempts, final cytology, management plan, and clinical outcome were recorded. Follow-up records were available for between 2 and 7 years.

RESULTS

Following exclusions, 136 patients were found to have incidental thyroid avidity on their 18 F-FDG PET-CT. A total of 50 of these patients proceeded to thyroid ultrasound assessment. Of these, 37 patients underwent FNA (average 1.3 FNA attempts) with 17 having atypical cytology and 6 diagnosed with an incidental thyroid cancer either by FNA or thyroidectomy. Four patients who underwent surgery had benign pathology. All thyroid cancers identified were indolent papillary cancers without any impact on the treatment plan or survival.

CONCLUSION

The clinical outcomes of patients with an established primary malignancy are determined by their primary cancer and not by incidentally detected thyroid cancer. It may therefore be reasonable not to formally investigate a proportion of incidental 18 F-FDG PET-CT positive thyroid nodules where added benefit is unlikely. In such cases, a 'watch-and-wait' approach to the thyroid might be considered more appropriate.

Consensus statement on the management of incidentally discovered FDG avid thyroid nodules in patients being investigated for other cancers

With the widespread use of 18F-fluorodeoxyglucose positron emission tomography (FDG PET/CT) in the investigation and staging of cancers, incidental discovery of FDG-avid thyroid nodules is becoming increasingly common, with a reported incidence in the range 1%-4% of FDG PET/CT scans. The risk of malignancy in an incidentally discovered FDG avid thyroid nodule is not clear due to selection bias in reported retrospective series but is likely to be less than 15%. Even in cases where the nodule is found to be malignant, the majority will be differentiated thyroid cancers with an excellent prognosis even without treatment. If, due to index cancer diagnosis, age and co-morbidities, it is unlikely that the patient will survive 5 years, further investigation of an incidental FDG avid thyroid nodule is unlikely to be warranted. We provide a consensus statement on the circumstances in which further investigation of FDG avid thyroid nodules with ultrasound and fine needle aspiration might be appropriate.

Patient Compliance With Surveillance of Thyroid Nodules Classified as Atypia of Undetermined Significance

OBJECTIVE

To determine whether thyroid nodule surveillance compliance is influenced by patient demographics or plan type.

STUDY DESIGN

Retrospective case series from 2010 to 2018.

SETTING

United States Military Health System.

METHODS

There were 481 patients with a thyroid nodule fine-needle aspiration classified as atypia of undetermined significance for whom treatment and follow-up information were available. Demographic information and surveillance plan type were extracted from the medical record and statistical analysis was performed to determine whether these characteristics influenced compliance rates.

RESULTS

A total of 289 nodules were surveilled and 192 diagnostic lobectomies were performed. An initial surveillance plan was documented in 93% (268/289) and 86% (231/268) complied. The most common plans were repeat biopsy in 78% (210/268) or ultrasound in 20% (53/268). A second plan was documented in 88% (204/231) of those who complied with the first. The most common second plans were ultrasound in 87% (178/204) or repeat biopsy in 8% (17/204). Compliance with the second plan was 64% (130/204), significantly lower than with the first (OR 3.6, 95% CI: [2.3, 5.6], P < .0001). Only 45% (130/289) were surveilled twice. Age and gender did not significantly affect compliance rates. Compliance with primary care ultrasound surveillance was 40% (21/52), significantly lower than with a specialist (77% [137/179]; OR 4.8, 95% CI: [2.5, 9.3, P < .0001).

CONCLUSION

Compliance with surveillance of thyroid nodules classified as atypia of undetermined significance was poor in this military cohort. Ultrasound surveillance by a specialist may be more reliable than with primary care.

Risk-stratification of thyroid nodules examined by 18FDG-PET/CT while ensuring congruity between imaging and histopathological localization

PURPOSE

The risk of malignancy (ROM) in FDG-avid thyroid incidentalomas varies between studies, which may be contributed by discordance between the anatomical localization depicted on ¹⁸FDG-PET/CT and by histopathological examination. The purpose was to ensure anatomical congruity between the index tumour identified by ¹⁸FDG-PET/CT and the histopathological examination, in order to assess the risk of malignancy (ROM) in PET-positive and PET-negative thyroid nodules. Further, preoperative characteristics indicative of thyroid malignancy were identified.

METHODS

Thirty-two patients referred to thyroid surgery were prospectively included. ¹⁸FDG-PET/CT, fine-needle aspiration biopsy and thyroid ultrasonography examination were performed in all participants. The exact anatomical localization of the index nodule was established by histopathological examination to ensure concordance with the ¹⁸FDG-PET/CT finding.

RESULTS

Forty thyroid nodules were included. Malignancy was identified in 10 of 28 PET-positive nodules and in 1 of 12 PET-negative nodules, resulting in a ROM of 36% and 8%, respectively. A Hurtle cell neoplasm was found in 50% of patients with a benign nodule and a PET-positive scan. One PET-negative nodule represented a papillary microcarcinoma. In PET-positive nodules, hypoechogenicity, irregular margins, and pathological lymph nodes on thyroid ultrasonography were characteristics associated with malignancy.

CONCLUSIONS

In this study-ensuring anatomical congruity between PET-findings and the histopathological examination-the risk of malignancy in PET-positive thyroid nodules was 36%. A low ROM was seen in thyroid nodules without suspicious ultrasonographic findings, independent of the ¹⁸FDG-PET/CT result.

TRIAL REGISTRATION NUMBER

NCT02150772 registered 14th of April 2014.

Radiomics Analysis of [18F]-Fluorodeoxyglucose-Avid Thyroid Incidentalomas Improves Risk Stratification and Selection for Clinical Assessment

Background: [¹⁸F]-Fluorodeoxyglucose (FDG)-avid thyroid lesions incidentally detected on positron emission tomography/computed tomography (PET/CT) scans represent a tumor lesion in about 30% of cases. The present study evaluated the ability of PET metrics and radiomics features to predict final diagnosis of [¹⁸F]FDG thyroid incidentalomas (TIs). Methods: A total of 104 patients with 107 TIs were retrospectively studied; 30 nodules (28%) were diagnosed as malignant. After volumetric segmentation of each thyroid lesion, metabolic tumor volume (MTV), total lesion glycolysis (TLG), standardized uptake values (SUVs), and metabolic heterogeneity were estimated, and 107 radiomics features were extracted following a standard protocol. Results: MTV, TLG, SUVmax, SUVmean, and SUVpeak among functional PET parameters, and gray-level co-occurrence matrix (GLCM)_InverseDifferenceMoment, shape_Sphericity, GLCM_SumSquares, firstorder_Maximum2DDiameterSlice, firstorder_Energy, and GLCM_Contrast among nonredundant radiomics features, showed significantly different values between malignant and benign TIs (Mann-Whitney U-test, p < 0.01 for all). Univariate logistic regression revealed that these parameters demonstrated good ability to predict final diagnosis of TIs (p < 0.02 for all). Shape_Sphericity was the best predictor classifying 82% of TIs correctly (p < 0.0001). Only TLG, SUVmax, and shape_Sphericity retained significance (p < 0.0001) by multivariate analysis. Malignant lesion prevalence increased from 7% to 100% in accordance with the number (score, 0-3) of the three positive parameters present (χ² trend, p < 0.0001). A score of 0 excludes malignant TIs with a negative predictive value of 93%, while a score of 3 predicted malignancy with a positive predictive value of 100%. Conclusions: PET metrics and radiomics analysis can improve identification of [¹⁸F]FDG-avid TIs at high risk of malignancy. A model based on TLG, SUVmax, and shape_Sphericity may allow prediction of a final diagnosis, providing useful information for the management of TIs.

Risk Stratification of 18F-Fluorodeoxyglucose-Avid Thyroid Nodules Based on ACR Thyroid Imaging Reporting and Data System

OBJECTIVE

Fine needle aspiration (FNA) of thyroid nodules is often requested based on ¹⁸F-fluorodeoxyglucose (FDG) uptake regardless of sonographic features. The purpose of this study is to determine the risk of malignancy in FDG-avid thyroid nodules when stratified according to the ACR Thyroid Imaging Reporting and Data System (TI-RADS).

METHODS

This retrospective study included patients who underwent ultrasound-guided FNA between January 1, 2010, and November 19, 2018, and PET/CT within 1 year before the FNA. In all, 170 nodules in 166 patients (65 men, 101 women, age 60.2 ± 14.3 years) were eligible for inclusion, of which 151 had a clearly benign or malignant histology. PET images were reviewed for maximum standardized uptake value and nodule location. Sonographic features and TI-RADS category were determined by three radiologists. Patient charts were reviewed for histology. Statistical analyses included risk of malignancy in FDG-avid nodules within each TI-RADS category.

RESULTS

Of the 151 nodules, 52 were malignant (34.4%). Malignancy risk was 0% in 1 TR1 nodule (compared with 0.3% in the published TI-RADS study), 16.7% in 6 TR2 nodules (compared with 1.5%), 13.2% in 38 TR3 nodules (compared with 4.8%), 23.7% in 59 TR4 nodules (compared with 9.1%), and 68.1% in 47 TR5 nodules (compared with 35.0%).

DISCUSSION

The majority (71%, 121 of 170) of FDG-avid thyroid nodules are TR4 and TR5, with rates of malignancy greater than those in the general TI-RADS population. ACR TI-RADS is helpful in stratification of FDG-avid nodules; the risk of malignancy in sonographically low-suspicion nodules (13.3%, 6 of 45) is significantly lower than high-suspicion nodules (43.4%, 46 of 106, P < .001).

Computer-Aided Diagnostic Technique in 2-Deoxy-2-[18F]fluoro-D-glucose-Positive Thyroid Nodule: Clinical Experience of 74 Non-thyroid Cancer Patients

This study verified the value of a computer-aided diagnosis (CAD) technique assisting in ultrasonography (US) diagnosis of 2-deoxy-2-[¹⁸F]fluoro-D-glucose (¹⁸FDG)-avid thyroid incidentalomas on positron emission tomography. A total of 82 ¹⁸FDG-avid thyroid incidentalomas from 74 non-thyroid cancer patients were retrospectively analyzed with respect to US and CAD parameters (anechoic area, hyper-echoic foci, hypo-echogenicity, heterogeneity, margin, taller-than-wide shape, eccentric area) and were compared with 38 other non-¹⁸FDG-avid nodules found in the same patient group. Fine-needle aspiration cytology or surgical intervention pathology was performed for diagnosis. No significant differences in nodule size or CAD parameters were found in ¹⁸FDG-avid nodules reported as benign, indeterminate or malignant. Significantly more taller-than-wide nodules were thyroid originating than metastatic (0.30 vs. 0.16, p < 0.05). Nevertheless, combined CAD and positron emission tomography/computed tomography scores and a discrimination point of 4 resulted in a sensitivity of 75% and a specificity of 80% in prediction of incidentaloma benignity.

Thyroid Incidentalomas Detected on 18F-Fluorodeoxyglucose Positron Emission Tomography with Computed Tomography: Malignant Risk Stratification and Management Plan

OBJECTIVE

The aims of this study were to stratify the risk of malignancy in thyroid incidentalomas detected on ¹⁸F-fluorodeoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) using ultrasound features according to guidelines for thyroid nodules and to develop a subsequent management plan.

METHODS

From a historical cohort of 96,942 consecutive patients who underwent ¹⁸F-FDG PET/CT between October 2008 and September 2015, 1342 patients with 1364 nodules underwent ultrasound evaluation for focal uptake in thyroid gland, with a final diagnosis made for 877 patients with 907 nodules, which were included in this study. Ultrasound images were retrospectively reviewed, and they were stratified according to the American Thyroid Association and Korean Thyroid Image Reporting and Data System guidelines. The calculated malignancy risks were compared with the estimated risks suggested by the guidelines.

RESULTS

The overall malignancy risk of thyroid incidentalomas detected on ¹⁸F-FDG PET/CT was 54.7%. When stratified according to the American Thyroid Association guidelines, the malignancy risks of thyroid incidentalomas with high and intermediate suspicion (93.2% and 45.2%, respectively) were higher than those indicated in the guidelines. The malignancy risks of thyroid incidentalomas with low and very low suspicion (8.1% and 0%, respectively) were within the guideline ranges. These findings were also noted when thyroid incidentalomas were stratified according to the Korean Thyroid Image Reporting and Data System, and in a subgroup of nodules >1 cm.

CONCLUSIONS

Ultrasound examinations can be used to stratify the malignancy risk of thyroid incidentalomas detected on ¹⁸F-FDG PET/CT. The risk of malignancy did not increase in thyroid incidentalomas with low and very low suspicion, indicating that only selective biopsies may be needed in these categories of thyroid incidentalomas.

Investigation of thyroid nodules: A practical algorithm and review of guidelines

BACKGROUND

High resolution ultrasound has led to early detection of subclinical tumors and drastic increase in incidence of thyroid malignancy. To achieve a balance in appropriate investigation without perpetuating an overdiagnosis phenomenon, a concise set of evidence-based recommendations to stratify risk is required.

METHODS

We sought to assemble an evidence-based diagnostic algorithm and accompanying pictorial review for workup of thyroid nodules that summarizes the most recent guidelines. In addition, we conducted a literature search and analysis of our imaging databases.

RESULTS

Although many imaging features of benign and malignant nodules can be nonspecific, others, such as microcalcifications, lymphadenopathy, and peripheral invasion, are highly suggestive of malignancy. The predictive values of salient imaging characteristics are presented.

CONCLUSION

Evidence-based guidelines are available such that a cost-effective algorithm for thyroid nodule workup can be devised. Conservative management with a focus on periodic monitoring is the working clinical consensus on the approach to thyroid nodules.

Intraoperative frozen section can be reduced in thyroid nodules classified as Bethesda categories V and VI

Intraoperative frozen section (FS) can be reduced during thyroid lobectomy according to the results of fine needle aspiration (FNA). We evaluated the role of intraoperative FS in thyroid nodules with different diagnostic categories of the Bethesda System for Reporting Thyroid Cytopathology by FNA. This retrospective study included 1,235 nodules collected via thyroidectomy with both preoperative FNA and intraoperative FS at the Second Affiliated Hospital of Zhejiang University School of Medicine, from January 2011 to January 2014. FNA cytological diagnosis was classified into six categories, based on the Bethesda system. The diagnostic findings of FNA cytology and FS histology were compared with the final histological results. 189 nodules were benign. The remainder were malignant. FS diagnosis was more accurate than FNA diagnosis for nodules classified as Bethesda Categories II, III, and IV (P < 0.05). However, the accuracy of FNA diagnosis in nodules assigned Bethesda Categories V and VI was significantly higher than that of FS (P < 0.05). FS appears be beneficial for thyroid nodules classified as Bethesda categories I through IV. FS may not be necessary in nodules diagnosed as Bethesda Categories V and VI.