Risk of malignancy in focal thyroid lesions identified by (18)F-fluorodeoxyglucose positron emission tomography or positron emission tomography/computed tomography: evidence from a large series of studies

Personalized Diagnosis in Differentiated Thyroid Cancers by Molecular and Functional Imaging Biomarkers: Present and Future

Personalized diagnosis can save unnecessary thyroid surgeries, in cases of indeterminate thyroid nodules, when clinicians tend to aggressively treat all these patients. Personalized diagnosis benefits from a combination of imagery and molecular biomarkers, as well as artificial intelligence algorithms, which are used more and more in our timeline. Functional imaging diagnosis such as SPECT, PET, or fused images (SPECT/CT, PET/CT, PET/MRI), is exploited at maximum in thyroid nodules, with a long history in the past and a bright future with many suitable radiotracers that could properly contribute to diagnosing malignancy in thyroid nodules. In this way, patients will be spared surgery complications, and apparently more expensive diagnostic workouts will financially compensate each patient and also the healthcare system. In this review we will summarize essential available diagnostic tools for malignant and benignant thyroid nodules, beginning with functional imaging, molecular analysis, and combinations of these two and other future strategies, including AI or NIS targeted gene therapy for thyroid carcinoma diagnosis and treatment as well.

Radiomics Analysis of [18F]FDG PET/CT Thyroid Incidentalomas: How Can It Improve Patients’ Clinical Management? A Systematic Review from the Literature

Background: We performed a systematic review of the literature to provide an overview of the application of PET-based radiomics of [18F]FDG-avid thyroid incidentalomas and to discuss the additional value of PET volumetric parameters and radiomic features over clinical data. Methods: The most relevant databases were explored using an algorithm constructed based on a combination of terms related to our subject and English-language articles published until October 2021 were considered. Among the 247 identified articles, 19 studies were screened for eligibility and 11 met the criteria, with 4 studies including radiomics analyses. Results: We summarized the available literature based on a study of PET volumetric parameters and radiomics. Ten articles provided accurate details about volumetric parameters and their prospective value in tumour assessment. We included the data provided by these articles in a sub-analysis, but could not obtain statistically relevant results. Four publications analyzed the diagnostic potential of radiomics and the possibility of creating precise predictive models, their corresponding quality score being assessed. Conclusions: The use of PET volumetric parameters and radiomics analysis in patients with [18F]FDG-avid thyroid incidentalomas outlines a great prospect in diagnosis and stratification of patients with malignant nodules and may represent a way of limiting the need for unnecessary invasive procedures; however, further studies need to be performed for a standardization of the method.

Detection of thyroiditis on PET/CT imaging: a systematic review

PURPOSE

The incidence and clinical significance of thyroiditis detected by molecular imaging methods is a clinical challenge that is not widely investigated in the literature. The aim of this systematic review was to analyze published data about the detection of thyroiditis on PET or PET/CT using different tracers.

METHODS

A comprehensive computer literature search of the Scopus, PubMed/MEDLINE, Embase, and Cochrane library databases was conducted up to November 2019 to find relevant papers on the detection of thyroiditis by PET/CT, the metabolic appearance, and the clinical significance.

RESULTS

Twenty-six articles were selected and retrieved in full-text version. From the analyses of these studies, the following main findings have been found. Diffuse thyroid uptake of PET tracers is a relatively frequent event, ranging from 0.4 to 46.2%, and it is commonly related to benign disease. Thyroiditis is the most frequent reason for diffuse increased thyroid ¹⁸F-FDG uptake. Cases of malignant disease with a pattern of diffuse ¹⁸F-FDG thyroid uptake are less frequent. Preliminary studies show a possible role of thyroiditis detected by ¹⁸F-FDG PET/CT in evaluating treatment response and as a prognostic marker in oncological patients treated with immunotherapy. However, further studies are needed.

CONCLUSIONS

Diffuse ¹⁸F-FDG thyroid uptake is a relatively rare event commonly due to benign diseases, among which thyroiditis is the most common. The rate of neoplastic disease with diffuse ¹⁸F-FDG thyroid uptake is very low. Diffuse ¹⁸F-FDG thyroid uptake requires further investigation and clinical evaluation for the correct diagnosis. Currently, cases of diffuse thyroid uptake with non-¹⁸F-FDG radiotracer are only anecdotal.

Evidence-Based Data About Prevalence and Risk of Malignancy of Thyroid Incidentalomas Detected by Different PET Radiopharmaceuticals

Background:

To date, several meta-analyses and systematic reviews have reported data about the prevalence and risk of malignancy of thyroid incidentalomas detected by different PET radiopharmaceuticals.

Objective:

This article aims to summarize the published evidence-based data about the prevalence and risk of malignancy of thyroid incidentalomas detected by different PET radiopharmaceuticals.

Methods:

A comprehensive computer literature search of systematic reviews and meta-analyses published up to July 2019 in PubMed/MEDLINE and Cochrane library databases regarding the prevalence and risk of malignancy of thyroid incidentalomas detected by different PET radiopharmaceuticals was carried out.

Results:

We have summarized the data about prevalence and risk of malignancy of thyroid incidentalomas detected by different PET radiopharmaceuticals (fluorine-18 fluorodeoxyglucose, radiolabelled choline and prostate-specific membrane antigen) taking into account 8 evidence-based articles.

Conclusion:

Evidence-based data demonstrated that thyroid incidentalomas detected by different PET radiopharmaceuticals are not infrequent and their risk of malignancy is not negligible, in particular if focal pattern is evident at PET, thus requiring further clinical and instrumental evaluation.

PET/CT in thyroid nodule and differentiated thyroid cancer patients. The evidence-based state of the art

A more conservative approach to the clinical management of thyroid nodules and differentiated thyroid cancer has recently been proposed by the 2015 ATA guidelines. In this context, fine-needle aspiration biopsy has been reserved for nodules with particular ultrasound features or dimensions that exclude low-risk thyroid lesions. Accordingly, a less aggressive surgical approach (i.e. lobectomy) has been recommended as the first-choice treatment in nodules with indeterminate cytology or in small cytologically confirmed malignant nodules. At the same time, radioactive remnant ablation has been considered only for DTC patients with concrete risks of disease persistence/relapse after thyroidectomy. In addition, further radioactive iodine therapies (RAI) have been proposed only for patients presenting unresectable and iodine-avid structural relapse. In this complex scenario, which requires attention to each clinical aspect of the patient, the introduction of accurate diagnostic tools is highly warranted. PET/CT is a very sensitive and specific diagnostic procedure that can better characterize the risk of thyroid nodules, identify DTC relapse early and predict the response to RAI. Thus, it seems essential to customize a more conservative approach to thyroid nodules and DTC patients. The aim of this review is to report the principal clinical context in which PET/CT has been used and to evaluate the evidence-based support for each diagnostic indication.

Fine-needle aspiration in all thyroid incidentalomas at 18 F-FDG PET/CT: Can EU-TIRADS revise the dogma?

OBJECTIVE

Focal thyroid incidentalomas (TIs) are observed in 2% of ¹⁸ F-FDG PET/CT representing malignancy in one-third of cases. Currently, due to the lack of evidence on their optimal management, guidelines suggest fine-needle aspiration cytology (FNAC). The study aim was to evaluate the role of ultrasound evaluation according to EU-TIRADS to assess the risk of TIs and inform FNAC prescriptions.

DESIGN

We retrospectively reviewed ¹⁸ F-FDG PET/CT TIs recorded during the period 2014-2017. Enrolled were TIs with histological outcome and autonomous nodules. Cases with uncertain matching between ¹⁸ F-FDG PET/CT, ultrasound and histology were excluded.

RESULTS

According to the selection criteria, 75 TIs, being 13 (17.3%) malignant and 62 (82.7%) benign, were included. Cancers had significantly higher SUVmax and SUVmax ratio (Mann-Whitney P < 0.01) than benign, and the most accurate cut-offs were >7.1 and >3.65, respectively. At ultrasound, the cancer rate was 0% in EU-TIRADS 2, 2.9% in EU-TIRADS 3, 4.2% in EU-TIRADS 4% and 78.6% in EU-TIRADS 5 (chi-squared P < 0.001). Sensitivity, specificity, PPV, NPV and accuracy for malignancy were 92%, 64%, 35%, 98% and 69% for SUVmax; 85%, 68%, 36%, 96% and 71% for SUVmax ratio; and 85%, 95%, 79%, 97% and 93% for EU-TIRADS, respectively. The absence of all these three features reached a specificity of 97.1%.

CONCLUSIONS

EU-TIRADS, within a clinical careful approach, can discriminate with significant accuracy lesions at high risk of malignancy from those at low risk among TIs at ¹⁸ F-FDG PET/CT. Additionally, a centre-based threshold for SUV parameters should be useful for the initial assessment of these lesions during PET/CT reading and reporting.

Systematic reviews of diagnostic tests in endocrinology: an audit of methods, reporting, and performance

BACKGROUND

Systematic reviews provide clinicians and policymakers estimates of diagnostic test accuracy and their usefulness in clinical practice. We identified all available systematic reviews of diagnosis in endocrinology, summarized the diagnostic accuracy of the tests included, and assessed the credibility and clinical usefulness of the methods and reporting.

METHODS

We searched Ovid MEDLINE, EMBASE, and Cochrane CENTRAL from inception to December 2015 for systematic reviews and meta-analyses reporting accuracy measures of diagnostic tests in endocrinology. Experienced reviewers independently screened for eligible studies and collected data. We summarized the results, methods, and reporting of the reviews. We performed subgroup analyses to categorize diagnostic tests as most useful based on their accuracy.

RESULTS

We identified 84 systematic reviews; half of the tests included were classified as helpful when positive, one-fourth as helpful when negative. Most authors adequately reported how studies were identified and selected and how their trustworthiness (risk of bias) was judged. Only one in three reviews, however, reported an overall judgment about trustworthiness and one in five reported using adequate meta-analytic methods. One in four reported contacting authors for further information and about half included only patients with diagnostic uncertainty.

CONCLUSION

Up to half of the diagnostic endocrine tests in which the likelihood ratio was calculated or provided are likely to be helpful in practice when positive as are one-quarter when negative. Most diagnostic systematic reviews in endocrine lack methodological rigor, protection against bias, and offer limited credibility. Substantial efforts, therefore, seem necessary to improve the quality of diagnostic systematic reviews in endocrinology.

Thyroid incidentalomas on 18FDG-PET/CT: a metabolico-pathological correlation

Background

Thyroid incidentaloma is defined as an unsuspected thyroid lesion found on imaging study or while performing a surgery non-related to the thyroid gland. Most recent scientific literature tends to demonstrate a detection rate of 0.1–4.3% for incidental findings of thyroid focal uptake identified by ¹⁸F-fluorodeoxyglugose Positron Emission Tomography with computed tomography (¹⁸FDG-PET/CT) initially prescribed for nonthyroid disease. From 10.3 to 80.0% of patients who underwent further evaluation are diagnosed with malignant lesions.

Our first objective is to determine the risk of malignancy confined in thyroid incidentalomas(IT) detected on ¹⁸FDG-PET/CT in patients treated in a tertiary care center (Centre Hospitalier Universitaire de Sherbrooke). Second, we want to identify a cut-off value for SUVmax in order to distinguish benign from malignant IT. Third, we look for predictive criterion that can be outlined to help in their management.

Methods

We retrospectively reviewed 40 914 charts of patients who had a ¹⁸FDG-PET/CT done in a tertiary center from 2004 to 2014. For each patient where a thyroid incidentaloma has been identified, Maximum Standardized Uptake Value (SUVmax), ultrasound report, cytology and histopathological results as well as oncologic outcomes were compiled and analyzed.

Results

In this study, the incidence for thyroid incidentaloma detected with ¹⁸FDG-PET/CT is 0.74%. The rate of malignancy present in IT is 8.2% based on histopathological results. Of the patients who underwent surgery, thyroid malignancy was identified in 54.3% of them. Cytoponction showed a strong correlation with final histopathological results (p = 0.009).

Conclusion

Thyroid incidentalomas detected with ¹⁸FDG-PET/CT are relatively infrequent, but the potential risk of malignancy remains elevated. Fine needle aspiration biopsy is the investigation of choice to rule out a malignant incidentaloma when there is no other element in the clinical portrait to preclude such additional work up.

Incidence and Significance of Incidental Focal Thyroid Uptake on (18)F-FDG PET Study in a Large Patient Cohort: Retrospective Single-Centre Experience in the United Kingdom

OBJECTIVE

To assess the prevalence and pathological nature of incidental focal thyroid uptake on (18)F-FDG (2-[(18)F]-fluoro-2-deoxy-D-glucose) PET (positron emission tomography) and examine the role of the maximum standardised uptake value (SUVmax) to differentiate benign from malignant thyroid pathology.

MATERIAL AND METHODS

(18)F-FDG PET reports were retrospectively reviewed. Incidental focal tracer uptake in the thyroid was noted in 147 patients (0.5%). Patients with known primary thyroid malignancy were excluded. The final diagnosis was made following ultrasonography of the neck, fine-needle aspiration cytology (FNAC) or histopathology of the surgically resected specimen where surgery was indicated. A Mann-Whitney U test was used to compare the SUVmax of benign and malignant thyroid pathology. Receiver operating characteristic (ROC) analysis was performed to identify an SUVmax cutoff in differentiating benign from malignant pathology.

RESULTS

A final diagnosis was achieved in 47/147 (32%) of the patients. The diagnoses included benign lesions in 36 patients and malignancy in 9 patients. In 2 patients, FNAC demonstrated indeterminate follicular lesions; however, surgical excision was not performed. There was a highly significant difference in the mean SUVmax of malignant focal thyroid uptake (15.7 ± 5.9) compared to that of benign lesions (7.1 ± 6.8) with a p value of 0.000123. An SUVmax of 9.1 achieved a sensitivity of 81.6%, specificity of 100% and area under the curve of 0.915 in the ROC analysis differentiating benign from malignant disease.

CONCLUSION

The malignancy potential of incidental focal thyroid uptake remains high and warrants prompt and appropriate follow-up by the clinician. The SUVmax may aid in further characterisation of the lesion and its management.