Malignancy risk of initially benign thyroid nodules: validation with various Thyroid Imaging Reporting and Data System guidelines

Diagnostic Performance of Six Ultrasound Risk Stratification Systems for Thyroid Nodules: A Systematic Review and Network Meta-Analysis

BACKGROUND. Risk stratification systems for evaluating thyroid nodules on ultrasound use varying approaches to classify levels of suspicion for malignancy, leading to variable performance. OBJECTIVE. The purpose of this study was to perform a network meta-analysis comparing six risk stratification systems used to evaluate thyroid nodules on ultrasound in terms of their diagnostic performance for the detection of thyroid cancer. EVIDENCE ACQUISITION. Five bibliometric databases were searched for studies published through August 31, 2022, that compared at least two of six ultrasound risk stratification systems (the American Association of Clinical Endocrinologists, American College of Endocrinology, and Associazione Medici Endocrinologi [AACE/ACE/AME] system; American College of Radiology Thyroid Imaging Reporting and Data System [ACR TI-RADS]; the American Thyroid Association [ATA] risk stratification system; European Thyroid Association Thyroid Imaging Reporting and Data System [EU-TIRADS]; the Korean Thyroid Imaging Reporting and Data System [K-TIRADS] endorsed by the Korean Thyroid Association and the Korean Society of Thyroid Radiology; and the Thyroid Imaging Reporting and Data System developed by Kwak et al. [Kwak TIRADS]) in terms of their diagnostic performance for the detection of thyroid cancer, with cytologic or histologic evaluation used as a reference standard. The studies' risk of bias was evaluated using the Newcastle-Ottawa Scale. A meta-analysis of each system was performed to identify the risk category threshold that had the highest accuracy as well as the highest sensitivity and specificity at this threshold. Network meta-analysis was used to perform hierarchic ranking and identify the systems having the highest sensitivities and specificities at each system's most accurate threshold. EVIDENCE SYNTHESIS. The analysis included 39 studies with 49,661 patients. All studies were of fair (n = 17) or good (n = 22) quality. The most accurate risk category thresholds were class 3 (high risk) for the AACE/ACE/AME system, TR5 (highly suspicious) for ACR TI-RADS, EU-TIRADS 5 (high risk) for EU-TIRADS, 4c (moderate concern but not classic for malignancy) for Kwak TIRADS, K-TIRADS 5 (high suspicion) for K-TIRADS, and high suspicion for the ATA system. At these thresholds, the systems had sensitivity of 64-77% and specificity of 82-90%. Network meta-analysis identified the highest sensitivity and highest specificity for ACR TI-RADS, followed by K-TIRADS. CONCLUSION. Of six risk stratification systems, ACR TI-RADS had the highest diagnostic performance for the detection of thyroid nodules on ultrasound. CLINICAL IMPACT. This network meta-analysis can inform decisions regarding implementation of the risk stratification systems and can aid future system updates.

Diagnostic Performance of Various Ultrasound Risk Stratification Systems for Benign and Malignant Thyroid Nodules: A Meta-Analysis

BACKGROUND

To evaluate the diagnostic performance of ultrasound risk-stratification systems for the discrimination of benign and malignant thyroid nodules and to determine the optimal cutoff values of individual risk-stratification systems.

METHODS

PubMed, Embase, SCOPUS, Web of Science, and Cochrane library databases were searched up to August 2022. Sensitivity and specificity data were collected along with the characteristics of each study related to ultrasound risk stratification systems.

RESULTS

Sixty-seven studies involving 76,512 thyroid nodules were included in this research. The sensitivity, specificity, diagnostic odds ratios, and area under the curves by K-TIRADS (4), ACR-TIRADS (TR5), ATA (high suspicion), EU-TIRADS (5), and Kwak-TIRADS (4b) for malignancy risk stratification of thyroid nodules were 92.5%, 63.5%, 69.8%, 70.6%, and 95.8%, respectively; 62.8%, 89.6%, 87.2%, 83.9%, and 63.8%, respectively; 20.7111, 16.8442, 15.7398, 12.2986, and 38.0578, respectively; and 0.792, 0.882, 0.859, 0.843, and 0.929, respectively.

CONCLUSION

All ultrasound-based risk-stratification systems had good diagnostic performance. Although this study determined the best cutoff values in individual risk-stratification systems based on statistical assessment, clinicians could adjust or alter cutoff values based on the clinical purpose of the ultrasound and the reciprocal changes in sensitivity and specificity.

Validating and Comparing C-TIRADS, K-TIRADS and ACR-TIRADS in Stratifying the Malignancy Risk of Thyroid Nodules

The thyroid imaging reporting and data system (TIRADS) was proposed by experts for optimal ultrasound evaluation of malignancy risk of thyroid focal lesions. There are several versions of TIRADS, some of them have been validated sufficiently, and the others have not been well assessed. In this study, a recently launched Chinese version of TIRADS (C-TIRADS) for malignancy risk stratification of thyroid nodules was validated, and the performance was compared to that of the Korean TIRADS (K-TIRADS) and American College of Radiology(ACR) TIRADS (ACR-TIRADS). Archives of 2177 patients who had undergone thyroid ultrasound examination, coarse needle tissue biopsy and/or surgery were reviewed, and 1978 patients with 1982 thyroid nodules were assessed according to the three TIRADSs. The histopathology was taken as the golden standard. The results showed the 1982 thyroid nodules were consisted of 1306 benign nodules and 676 malignant nodules. The malignancy risk accounted for 1.09%, 2.14%, 10.34%, 49.28%, 88.19% and 85.29% of the total nodules that were categorised as C-TIRADS 2, 3, 4A, 4B, 4C and 5, respectively; 0.00%, 1.64%, 2.87%,18.71% and 82.22% of the total nodules that were categorised as ACR-TIRADS 1, 2, 3, 4 and 5, respectively; 0.85%, 3.27%, 24.27% and 80.96% of the total nodules that were categorised as K-TIRADS 2, 3, 4 and 5, respectively. The correlation between the category of TIRADS and percentile of malignancy was 0.94 in the C-TIRADS, 1.00 in the ACR-TIRADS, and 1.00 in the K-TIRADS, respectively. The highest values of accuracy(AUC) of ROC curves of C-TIRADS 4B, K-TIRADS 5 and ACR-TIRADS 5 were taken as the cut-off values for risk stratification, respectively. The sensitivity, specificity, positive and negative predictive values and AUC by C-TIRADS 4B, K-TIRADS 5 and ACR-TIRADS 5 for malignancy risk stratification of thyroid nodules were 90.83%, 84.23%, 74.88% and 94.66% and 0.88, respectively; 83.58%, 89.82%, 80.95%, 91.36% and 0.87, respectively; and 85.50%, 90.35%, 82.10%, 92.33% and 0.88, respectively (P>0.05 for all). We concluded that the C-TIRADS has excellent performance in the malignancy risk stratification of thyroid nodules by the optimized cut-off value, which is comparable to that in K-TIRADS and ACR-TIRADS.

Repeat thyroid FNAC: Inter-observer agreement among high- and low-volume centers in Naples metropolitan area and correlation with the EU-TIRADS

Our institution (University Hospital "L. Vanvitelli" - Naples, Italy) is a high-volume (HV) center in Naples metropolitan area and many patients are referred there to repeat thyroid fine-needle aspiration cytology (FNAC) after initial FNAC performed in low-volume institutions (LV). The aims of the study were to 1) examine the inter-observer agreement between HV and LV institutions according to the Italian thyroid cytology system, and 2) explore how the discordant FNAC reports were distributed in the European Thyroid Imaging and Reporting Data System (EU-TIRADS) categories. All consecutive cases of repeat FNAC performed at University Hospital "L. Vanvitelli" from January 2016 to December 2021 were retrospectively reviewed. Fleiss' kappa (κ) was used to assess the inter-observer agreement, and categorical variables were compared by chi-square testing. P < 0.05 was considered statistically significant. A total of 124 nodules from 124 adults (mean age 49 years; mean maximum diameter 19 mm) were evaluated. Initial FNAC reports at LV were: 4 (3.2%) TIR1c, 64 (51.6%) TIR2, 48 (38.7%) TIR3A, 8 (6.5%) TIR3B, 0 TIR4, 0 TIR5. The overall FNAC reports were significantly different between the LV and HV institutions. At repeated FNAC, cytological diagnosis was unchanged in 64 (51.6%) cases including TIR2 and TIR3A results. A downgraded FNAC diagnosis (i.e., TIR2 vs TIR3A, TIR2 vs TIR3B) was observed in 36 (29%) nodules. An upgraded FNAC diagnosis (i.e., TIR3B vs TIR2, TIR3B vs TIR3A, TIR4 vs TIR3A, TIR5 vs TIR2, TIR5 vs TIR3B) was recorded in 24 (19.4%) nodules. The weighted inter-observer agreement between LV and HV institutions was poor (κ=0.133). Changed FNAC results were significantly (p=0.0023) more frequent in nodules at intermediate/high-risk (i.e., EU-TIRADS 4/5) than in those at no/low risk (EU-TIRADS 2/3) [i.e., 32/48 (66.7%) and 28/76 (36.8%), respectively]. Downgraded FNAC results were significantly more frequent in EU-TIRADS 2/3 (p=0.001) while upgraded FNAC were present only in EU-TIRADS 4/5 (24/24, 100.0%). The inter-observer agreement among LV and HV thyroid services was poor. The EU-TIRADS 4 and 5 categories included all the malignant nodules with FNAC results reclassified as higher risk (i.e., TIR3B-TIR4-TIR5) by the high-volume cytology service.

Diagnostic Performance of Kwak, EU, ACR, and Korean TIRADS as Well as ATA Guidelines for the Ultrasound Risk Stratification of Non-Autonomously Functioning Thyroid Nodules in a Region with Long History of Iodine Deficiency: A German Multicenter Trial

Germany has a long history of insufficient iodine supply and thyroid nodules occur in over 30% of the adult population, the vast majority of which are benign. Non-invasive diagnostics remain challenging, and ultrasound-based risk stratification systems are essential for selecting lesions requiring further clarification. However, no recommendation can yet be made about which system performs the best for iodine deficiency areas. In a German multicenter approach, 1211 thyroid nodules from 849 consecutive patients with cytological or histopathological results were enrolled. Scintigraphically hyperfunctioning lesions were excluded. Ultrasound features were prospectively recorded, and the resulting classifications according to five risk stratification systems were retrospectively determined. Observations determined 1022 benign and 189 malignant lesions. The diagnostic accuracies were 0.79, 0.78, 0.70, 0.82, and 0.79 for Kwak Thyroid Imaging Reporting and Data System (Kwak-TIRADS), American College of Radiology (ACR) TI-RADS, European Thyroid Association (EU)-TIRADS, Korean-TIRADS, and American Thyroid Association (ATA) Guidelines, respectively. Receiver Operating Curves revealed Areas under the Curve of 0.803, 0.795, 0.800, 0.805, and 0.801, respectively. According to the ATA Guidelines, 135 thyroid nodules (11.1%) could not be classified. Kwak-TIRADS, ACR TI-RADS, and Korean-TIRADS outperformed EU-TIRADS and ATA Guidelines and therefore can be primarily recommended for non-autonomously functioning lesions in areas with a history of iodine deficiency.

Multimodal imaging of thyroid cancer

PURPOSE OF REVIEW

Thyroid cancer is the most common endocrine cancer in adults with rising incidence. Challenges in imaging thyroid cancer are twofold: distinguishing thyroid cancer from benign thyroid nodules, which occur in 50% of the population over 50 years; and correct staging of thyroid cancer to facilitate appropriate radical surgery in a single session. The clinical management of thyroid cancer patients has been covered in detail by the 2015 guidelines of the American Thyroid Association (ATA). The purpose of this review is to state the principles underlying optimal multimodal imaging of thyroid cancer and aid clinicians in avoiding important pitfalls.

RECENT FINDINGS

Recent additions to the literature include assessment of ultrasound-based scoring systems to improve selection of nodules for fine needle biopsy (FNB) and the evaluation of new radioactive tracers for imaging thyroid cancer.

SUMMARY

The mainstay of diagnosing thyroid cancer is thyroid ultrasound with ultrasound-guided FNB. Contrast-enhanced computed tomography and PET with [F]-fluorodeoxyglucose (FDG) and MRI are reserved for advanced and/or recurrent cases of differentiated thyroid cancer and anaplastic thyroid cancer, while [F]FDOPA and [Ga]DOTATOC are the preferred tracers for medullary thyroid cancer.

Contemporary Thyroid Nodule Evaluation and Management

CONTEXT

Approximately 60% of adults harbor 1 or more thyroid nodules. The possibility of cancer is the overriding concern, but only about 5% prove to be malignant. The widespread use of diagnostic imaging and improved access to health care favor the discovery of small, subclinical nodules and small papillary cancers. Overdiagnosis and overtreatment is associated with potentially excessive costs and nonnegligible morbidity for patients.

EVIDENCE ACQUISITION

We conducted a PubMed search for the recent English-language articles dealing with thyroid nodule management.

EVIDENCE SYNTHESIS

The initial assessment includes an evaluation of clinical risk factors and sonographic examination of the neck. Sonographic risk-stratification systems (e.g., Thyroid Imaging Reporting and Data Systems) can be used to estimate the risk of malignancy and the need for biopsy based on nodule features and size. When cytology findings are indeterminate, molecular analysis of the aspirate may obviate the need for diagnostic surgery. Many nodules will not require biopsy. These nodules and those that are cytologically benign can be managed with long-term follow-up alone. If malignancy is suspected, options include surgery (increasingly less extensive), active surveillance or, in selected cases, minimally invasive techniques.

CONCLUSION

Thyroid nodule evaluation is no longer a 1-size-fits-all proposition. For most nodules, the likelihood of malignancy can be confidently estimated without resorting to cytology or molecular testing, and low-frequency surveillance is sufficient for most patients. When there are multiple options for diagnosis and/or treatment, they should be discussed with patients as frankly as possible to identify an approach that best meets their needs.

Imaging, biopsy and non-surgical treatment of thyroid lesions: where are we at?

KEY POINTS

• Ultrasound is the prevalent modality for assessment of the thyroid and biopsy guidance of lesions. • The various TI-RADS classifications provide scoring systems which help indicate the likelihood of malignancy. • Ongoing research helps to improve the characterisation of nodules, biopsy techniques and non-surgical treatment methods.

A retrospective study of reducing unnecessary thyroid biopsy for American College of Radiology Thyroid Imaging Reporting and Data Systems 4 assessment through applying shear wave elastography

Objective The purpose of the study is to quantitatively assess shear-wave elastography (SWE) value in American College of Radiology Thyroid Imaging Reporting and Data Systems (ACR TI-RADS) 4. Materials and methods One hundred and fifty-two ACR TI-RADS 4 thyroid nodules undergoing SWE were included in the study. The mean (EMean), minimum (EMin) and maximum (EMax) of SWE elasticity were measured. Results The areas under the receiver operating characteristic (ROC) curves for SWE EMean, EMin and EMax in detecting benign and malignant nodules were 0.95, 0.83 and 0.84, respectively. Cut-off value of EMean ≤ 23.30 kPa is able to downgrade the lesion category to ACR TI-RADS 3 and cut-off value of EMean ≥ 52.14 kPa is able to upgrade the lesion category to ACR TI-RADS 5. Conclusions The EMean of SWE will probably identify nodules that have a high potential for benignity in ACR TI-RADS 4. It may help identify and select benign nodules while reducing unnecessary biopsy of benign thyroid nodules.

Fine-Needle Aspiration of Subcentimeter Thyroid Nodules in the Real-World Management

BACKGROUND

The Korea Thyroid Association published the revised guidelines for thyroid nodules in 2016. However, whether fine-needle aspiration is accurately performed based on indications and whether the results of this procedure are appropriately addressed according to clinical guidelines, particularly in subcentimeter nodules, are unclear.

METHODS

We retrospectively analyzed the fine-needle aspiration data of 331 thyroid nodules of patients who were referred to a tertiary hospital clinic for fine-needle aspiration. Each nodule was categorized according to ultrasonography findings based on the recommendations of the Korea Thyroid Association for fine-needle aspiration. Only nodules with a final pathological diagnosis of benign or malignant made using the Bethesda system were included.

RESULTS

Up to 32% of thyroid nodules that were not indicated for fine-needle aspiration were aspirated. Regarding subcentimeter nodules, only 28 of 123 (22.8%) aspirated nodules were indicated for fine-needle aspiration. Of the 49 malignant subcentimeter nodules, 33 (67.3%) underwent immediate surgery. Meanwhile, 14 (28.6%) nodules were lost to follow-up, and two (4.1%) were under active surveillance. Eighteen (36.7%) malignant subcentimeter nodules were not indicated for fine-needle aspiration but underwent surgical resection instead of active surveillance.

CONCLUSION

Despite the recommendations in the revised guidelines, several thyroid nodules that do not meet the indications for FNA are aspirated in real-world practice. To reduce overtreatment, a widespread knowledge of the correct indications for fine-needle aspiration is important in clinical practice, particularly for subcentimeter nodules.

A multicentre validation study for the EU-TIRADS using histological diagnosis as a gold standard

OBJECTIVE

Many systems for risk stratification of thyroid nodule with ultrasound (US) have been proposed and the EU-TIRADS issued by the ETA in 2017 was the last to have been published. The present study was undertaken to evaluate whether the malignancy risk of each category corresponded to the given range of the guidelines and assess the diagnostic value of EU-TIRADS in a multi-institutional trial with histology as gold standard.

DESIGN

Three institutions in Switzerland, France and United Kingdom shared this retrospective study. Enrolment period was 2013-2017. Included were patients who had undergone surgery with a detailed preoperative thyroid US.

METHODS

Cancer risk was calculated for each EU-TIRADS score. Predictivity tests were estimated. Nonparametric statistical analysis was used.

RESULTS

The final series included 1058 nodules of which 257 (24.3%) carcinomas. Nodules were classified as EU-TIRADS 2, 3, 4 and 5 in 6.7, 46.4, 26.2 and 20.7%, respectively. Cancer prevalence was 1.4, 3.5, 17 and 87.7% in classes 2-5, respectively (P < 0.0001). EU-TIRADS 5 had a significantly higher cancer rate than the other summed categories (7.7%; P < 0.0001) with OR 84.7. When EU-TIRADS 4 and 5 were combined, 93% sensitivity and 97% NPV were found and findings of the three institutions were quite similar. Using the recommended criteria for FNA negative predictive value was 90.9%.

CONCLUSIONS

The cancer rate was within or close to the given range described in the EU-TIRADS guidelines. The diagnostic value was satisfactory. The results were similar in the three institutions participating in the study.

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

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 ¹⁸ F-FDG PET/CT in stratifying the risk of malignancy in these lesions.

METHODS

Two institutions participated to this retrospective study in which a dedicated ¹⁸ F-FDG PET/CT was proposed to patients having a thyroid nodule with US assessment of EU-TIRADS 4 or 5. ¹⁸ F-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, ¹⁸ F-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, ¹⁸ F-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 ¹⁸ F-FDG PET/CT showed 85.7% sensitivity and 41.4% specificity.

CONCLUSIONS

¹⁸ F-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 ¹⁸ F-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.