Quantitative classification and radiomics of [18F]FDG-PET/CT in indeterminate thyroid nodules

Theranostics of Thyroid Cancer

Molecular imaging is pivotal in evaluating and managing patients with different thyroid cancer histotypes. The existing, pathology-based, risk stratification systems can be usefully refined, by incorporating tumor-specific molecular and molecular imaging biomarkers with theranostic value, allowing patient-specific treatment decisions. Molecular imaging with different radioactive iodine isotopes (ie, I131, I123, I124) is a central component of differentiated carcinoma (DTC)'s risk stratification while [18F]F-fluorodeoxyglucose ([18F]FDG) PET/CT is interrogated about disease aggressiveness and presence of distant metastases. Moreover, it is particularly useful to assess and risk-stratify patients with radioiodine-refractory DTC, poorly differentiated, and anaplastic thyroid cancers. [18F]F-dihydroxyphenylalanine (6-[18F]FDOPA) PET/CT is the most specific and accurate molecular imaging procedure for patients with medullary thyroid cancer (MTC), a neuroendocrine tumor derived from thyroid C-cells. In addition, [18F]FDG PET/CT can be used in patients with more aggressive clinical or biochemical (ie, serum markers levels and kinetics) MTC phenotypes. In addition to conventional radioiodine therapy for DTC, new redifferentiation strategies are now available to restore uptake in radioiodine-refractory DTC. Moreover, peptide receptor theranostics showed promising results in patients with advanced and metastatic radioiodine-refractory DTC and MTC, respectively. The current appropriate role and future perspectives of molecular imaging and theranostics in thyroid cancer are discussed in our present review.

Molecular imaging of thyroid and parathyroid diseases

INTRODUCTION

Molecular imaging of thyroid and parathyroid diseases has changed in recent years due to the introduction of new radiopharmaceuticals and new imaging techniques. Accordingly, we provided an clinicians-oriented overview of such techniques and their indications.

AREAS COVERED

A review of the literature was performed in the PubMed, Web of Science, and Scopus without time or language restrictions through the use of one or more fitting search criteria and terms as well as through screening of references in relevant selected papers. Literature up to and including December 2023 was included. Screening of titles/abstracts and removal of duplicates was performed and the full texts of the remaining potentially relevant articles were retrieved and reviewed.

EXPERT OPINION

Thyroid and parathyroid scintigraphy remains integral in patients with thyrotoxicosis, thyroid nodules, differentiated thyroid cancer and, respectively, hyperparathyroidism. In the last years positron-emission tomography with different tracers emerged as a more accurate alternative in evaluating indeterminate thyroid nodules [18F-fluorodeoxyglucose (FDG)], differentiated thyroid cancer [124I-iodide, 18F-tetrafluoroborate, 18F-FDG] and hyperparathyroidism [18F-fluorocholine]. Other PET tracers are useful in evaluating relapsing/advanced forms of medullary thyroid cancer (18F-FDOPA) and selecting patients with advanced follicular and medullary thyroid cancers for theranostic treatments (68Ga/177Ga-somatostatin analogues).

Combined clinical variable and radiomics of post-treatment total body scan for prediction of successful I-131 ablation in low-risk papillary thyroid carcinoma patients

To explore the feasibility of combined radiomics of post-treatment I-131 total body scan (TBS) and clinical parameter to predict successful ablation in low-risk papillary thyroid carcinoma (PTC) patients. Data of low-risk PTC patients who underwent total/near total thyroidectomy and I-131 ablation 30 mCi between April 2015 and July 2021 were retrospectively reviewed. The clinical factors studied included age, sex, and pre-ablative serum thyroglobulin (Tg). Radiomic features were extracted via PyRadiomics, and radiomic feature selection was performed. The predictive performance for successful ablation of the clinical parameter, radiomic, and combined models (radiomics combined with clinical parameter) was calculated using the area under the receiver operating characteristic curve (AUC). One hundred and thirty patients were included. Successful ablation was achieved in 77 patients (59.2%). The mean pre-ablative Tg in the unsuccessful group (15.50 ± 18.04 ng/ml) was statistically significantly higher than those in the successful ablation group (7.12 ± 7.15 ng/ml). The clinical parameter, radiomic, and combined models produced AUCs of 0.66, 0.77, and 0.87 in the training sets, and 0.65, 0.69, and 0.78 in the validation sets, respectively. The combined model produced a significantly higher AUC than that of the clinical parameter (p < 0.05). Radiomic analysis of the post-treatment TBS combined with pre-ablative serum Tg showed a significant improvement in the predictive performance of successful ablation in low-risk PTC patients compared to the use of clinical parameter alone.Thai Clinical Trials Registry TCTR identification number is TCTR20230816004 ( https://www.thaiclinicaltrials.org/show/TCTR20230816004 ).

Application of radiomics and machine learning to thyroid diseases in nuclear medicine: a systematic review

BACKGROUND

In the last years growing evidences on the role of radiomics and machine learning (ML) applied to different nuclear medicine imaging modalities for the assessment of thyroid diseases are starting to emerge. The aim of this systematic review was therefore to analyze the diagnostic performances of these technologies in this setting.

METHODS

A wide literature search of the PubMed/MEDLINE, Scopus and Web of Science databases was made in order to find relevant published articles about the role of radiomics or ML on nuclear medicine imaging for the evaluation of different thyroid diseases.

RESULTS

Seventeen studies were included in the systematic review. Radiomics and ML were applied for assessment of thyroid incidentalomas at 18 F-FDG PET, evaluation of cytologically indeterminate thyroid nodules, assessment of thyroid cancer and classification of thyroid diseases using nuclear medicine techniques.

CONCLUSION

Despite some intrinsic limitations of radiomics and ML may have affect the results of this review, these technologies seem to have a promising role in the assessment of thyroid diseases. Validation of preliminary findings in multicentric studies is needed to translate radiomics and ML approaches in the clinical setting.

Integrated Diagnostics of Thyroid Nodules

Thyroid nodules are common findings, particularly in iodine-deficient regions. Our paper aims to revise different diagnostic tools available in clinical thyroidology and propose their rational integration. We will elaborate on the pros and cons of thyroid ultrasound (US) and its scoring systems, thyroid scintigraphy, fine-needle aspiration cytology (FNAC), molecular imaging, and artificial intelligence (AI). Ultrasonographic scoring systems can help differentiate between benign and malignant nodules. Depending on the constellation or number of suspicious ultrasound features, a FNAC is recommended. However, hyperfunctioning thyroid nodules are presumed to exclude malignancy with a very high negative predictive value (NPV). Particularly in regions where iodine supply is low, most hyperfunctioning thyroid nodules are seen in patients with normal thyroid-stimulating hormone (TSH) levels. Thyroid scintigraphy is essential for the detection of these nodules. Among non-toxic thyroid nodules, a careful application of US risk stratification systems is pivotal to exclude inappropriate FNAC and guide the procedure on suspicious ones. However, almost one-third of cytology examinations are rendered as indeterminate, requiring "diagnostic surgery" to provide a definitive diagnosis. 99mTc-methoxy-isobutyl-isonitrile ([99mTc]Tc-MIBI) and [18F]fluoro-deoxy-glucose ([18F]FDG) molecular imaging can spare those patients from unnecessary surgeries. The clinical value of AI in the evaluation of thyroid nodules needs to be determined.

Molecular Diagnostics and [18F]FDG-PET/CT in Indeterminate Thyroid Nodules: Complementing Techniques or Waste of Valuable Resources?

Background: An accurate preoperative workup of cytologically indeterminate thyroid nodules (ITN) may rule out malignancy and avoid diagnostic surgery for benign nodules. This study assessed the performance of molecular diagnostics (MD) and 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG)-positron emission tomography/computed tomography (PET/CT) in ITN, including their combined use, and explored whether molecular alterations drive the differences in [18F]FDG uptake among benign nodules. Methods: Adult, euthyroid patients with a Bethesda III or IV thyroid nodule were prospectively included in this multicenter study. They all underwent MD and an [18F]FDG-PET/CT scan of the neck. MD was performed using custom next-generation sequencing panels for somatic mutations, gene fusions, and copy number alterations and loss of heterozygosity. Sensitivity, specificity, negative and positive predictive value (NPV, PPV), and benign call rate (BCR) were assessed for MD and [18F]FDG-PET/CT separately and for a combined approach using both techniques. Results: In 115 of the 132 (87%) included patients, MD yielded a diagnostic result on cytology. Sensitivity, specificity, NPV, PPV, and BCR were 80%, 69%, 91%, 48%, and 57% for MD, and 93%, 41%, 95%, 36%, and 32% for [18F]FDG-PET/CT, respectively. When combined, sensitivity and specificity were 95% and 44% for a double-negative test (i.e., negative MD plus negative [18F]FDG-PET/CT) and 68% and 86% for a double-positive test, respectively. Concordance was 63% (82/130) between MD and [18F]FDG-PET/CT. There were more MD-positive nodules among the [18F]FDG-positive benign nodules (25/59, 42%, including 11 (44%) isolated RAS mutations) than among the [18F]FDG-negative benign nodules (7/30, 19%, p = 0.02). In oncocytic ITN, the BCR of [18F]FDG-PET/CT was mere 3% and MD was the superior technique. Conclusions: MD and [18F]FDG-PET/CT are both accurate rule-out tests when unresected nodules that remain unchanged on ultrasound follow-up are considered benign. It may vary worldwide which test is considered most suitable, depending on local availability of diagnostics, expertise, and cost-effectiveness considerations. Although complementary, the benefits of their combined use may be confined when therapeutic consequences are considered, and should therefore not routinely be recommended. In nononcocytic ITN, sequential testing may be considered in case of a first-step MD negative test to confirm that withholding diagnostic surgery is oncologically safe. In oncocytic ITN, after further validation studies, MD might be considered. Clinical Trial Registration: This trial is registered with ClinicalTrials.gov: NCT02208544 (August 5, 2014), https://clinicaltrials.gov/ct2/show/NCT02208544.

68 Ga-FAPI-Avid Submental Ectopic Papillary Thyroid Carcinoma and Lateral Neck Lymphadenopathy With Low 18 F-FDG Uptake

ABSTRACT

Ectopic thyroid tissue is rare and generally occurs along the thyroglossal duct or in lateral cervical region. We reported 18 F-FDG and 68 Ga-FAPI findings of a 28-year-old woman with previously diagnosed BRAF -mutated lateral lymph node metastasis of unknown primary site. Low 18 F-FDG but increased 68 Ga-FAPI uptake was seen in a submental pretracheal nodular lesion. Postsurgical pathologic report verified the diagnosis of ectopic papillary thyroid carcinoma. High FAP expression in the tumor sample corresponded to its imaging manifestations.

The potential role of reprogrammed glucose metabolism: an emerging actionable codependent target in thyroid cancer

Although the incidence of thyroid cancer is increasing year by year, most patients, especially those with differentiated thyroid cancer, can usually be cured with surgery, radioactive iodine, and thyroid-stimulating hormone suppression. However, treatment options for patients with poorly differentiated thyroid cancers or radioiodine-refractory thyroid cancer have historically been limited. Altered energy metabolism is one of the hallmarks of cancer and a well-documented feature in thyroid cancer. In a hypoxic environment with extreme nutrient deficiencies resulting from uncontrolled growth, thyroid cancer cells utilize "metabolic reprogramming" to satisfy their energy demand and support malignant behaviors such as metastasis. This review summarizes past and recent advances in our understanding of the reprogramming of glucose metabolism in thyroid cancer cells, which we expect will yield new therapeutic approaches for patients with special pathological types of thyroid cancer by targeting reprogrammed glucose metabolism.

Molecular testing in indeterminate thyroid nodules: an additional tool for clinical decision-making

Thyroid nodules are commonly encountered in clinical practice, affecting up to 50% of the population. The large majority of thyroid lumps are benign incidental findings detected by imaging, while approximately 5-15% harbor malignancy. For a target patient's care, it is of paramount importance to identify and treat thyroid malignancy, while preventing unnecessary invasive surgery in patients with benign lesions. Although fine needle aspiration (FNA) associated with cytological examination provides malignant risk information, 20-30% of diagnoses fall into the "indeterminate thyroid nodule" (ITN) category. ITN clinical management remains a challenging issue for physicians since the ITN risk of malignancy varies from 5% to 40% and most thyroid nodules undergo overtreatment with surgery procedures. ITN molecular testing may better define malignant risk in the single nodule and is able to discriminate with accuracy benign from malignant nodules. Nowadays there are different technologies and different molecular panels, each with its own specificity, sensitivity and predictive values. In view of widespread introduction of molecular testing , some outstanding questions remain and are addressed in the present review such as the presence of molecular panels acting as "rule in" or "rule out" tools, the effective impact of testing results in the clinical decision-making process, and the prohibitive cost of commercial assays associated with the lack of test reimbursement in national health systems.

Prediction of Malignant Thyroid Nodules Using 18 F-FDG PET/CT-Based Radiomics Features in Thyroid Incidentalomas

OBJECTIVE

The purpose of the current study was to evaluate the diagnostic performances of 18 F-FDG PET/CT-based radiomics features for prediction of malignant thyroid nodules (TNs) in thyroid incidentaloma (TI).

METHODS

PubMed, Cochrane database, and EMBASE database, from the earliest available date of indexing through December 31, 2022, were searched for studies evaluating diagnostic performance of 18 F-FDG PET/CT-based radiomics features for prediction of malignant TNs in TI. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LRs; positive and negative LRs), and estimated pooled area under the curve.

RESULTS

Across 5 studies (518 patients), the pooled sensitivity of 18 F-FDG PET/CT was 0.77 (95% confidence interval [CI], 0.67-0.84), and a pooled specificity was 0.67. Likelihood ratio syntheses gave an overall positive LR of 2.3 (95% CI, 1.5-3.6) and negative LR of 0.35 (95% CI, 0.26-0.47). The pooled diagnostic odds ratio was 7 (95% CI, 4-12). The pooled area under the curve of fixed effects was 0.763 (95% CI, 0.736-0.791), and that of random effects was 0.763 (95% CI, 0.721-0.805).

CONCLUSION

18 F-FDG PET/CT-based radiomics features showed a good diagnostic performance for prediction of malignant TNs in TI.

Incidence of PSMA PET thyroid incidentaloma depends on analysis method and tracer

OBJECTIVE

To investigate the incidences of prostate-specific membrane antigen (PSMA) thyroid incidentaloma (PTI) using different methods to define PTI, to compare the incidence of PTI among different PSMA PET tracers, and to evaluate the clinical consequences of PTI.

METHODS

PSMA PET/CT scans in consecutive patients with primary prostate cancer were analyzed for the presence of PTI using a structured visual (SV) analysis reporting any elevated thyroidal uptake; a semi-quantitative (SQ) analysis using a SUVmax thyroid/bloodpool (t/b) ratio ≥ 2.0 as cutoff; and an analysis of PTI incidence in the clinical reports (RV analysis).

RESULTS

A total of 502 patients were included. The incidence of PTIs was 22% in the SV analysis, 7% in the SQ analysis, and 2% in the RV analysis. PTI incidences differed significantly from 29 to 64% (SQ, resp. SV analysis) for [¹⁸F]PSMA-1007, 7 to 23% for [⁶⁸Ga]PSMA-11, 2 to 8% for [¹⁸F]DCFPyL, and to 0% for [¹⁸F]PSMA-JK-7. The majority of PTI in the SV and SQ analyses consisted of diffuse (72-83%) and/or only slightly elevated thyroidal uptake (70%). Inter-observer agreement in the SV analysis was substantial (kappa = 0.76-0.78). During follow-up (median 16.8 months), there were no thyroid-related adverse events except in three patients.

CONCLUSIONS

The incidence of PTI varies greatly among different PSMA PET tracers and is strongly dependent on the analysis method applied. PTI may safely be restricted to focal thyroidal uptake with a SUVmax t/b ratio ≥ 2.0. The clinical pursuit of a PTI must be weighed up to the expected outcome of the underlying disease.

KEY POINTS

• Thyroid incidentalomas (PTIs) are recognized in PSMA PET/CT. • Incidence of PTI varies greatly among PET tracers and analysis methods. • Incidence of thyroid-related adverse events in PTI cases is low.

PET/CT May Assist in Avoiding Pointless Thyroidectomy in Indeterminate Thyroid Nodules: A Narrative Review

Indeterminate thyroid nodules (ITN) are commonly encountered among the general population, with a malignancy rate of 10 to 40%. However, many patients may be overtreated with futile surgery for benign ITN. To avoid unnecessary surgery, PET/CT scan is a possible alternative to help differentiate between benign and malignant ITN. In this narrative review, the major results and limitations of the most recent studies on PET/CT efficacy (from PET/CT visual assessment to quantitative PET parameters and recent radiomic features analysis) and on cost-effectiveness (compared to other alternatives (such as surgery)) are presented. PET/CT can reduce futile surgery with visual assessment (around 40%; if ITN ≥ 10 mm). Moreover, PET/CT conventional parameters and radiomic features extracted from PET/CT imaging can be associated together in a predictive model to rule out malignancy in ITN, with a high NPV (96%) when certain criteria are met. Even though promising results were obtained in these recent PET/CT studies, further studies are needed to enable PET/CT to become the definitive diagnostic tool once a thyroid nodule is identified as indeterminate.

Global thyroid cancer incidence trend and age-period-cohort model analysis based on Global Burden of Disease Study from 1990 to 2019

Background

In view of the rapid increase in the incidence of thyroid cancer (TC) and the spread of overdiagnosis around the world, the quantitative evaluation of the effect of age, period and birth cohort on the incidence of TC, and the analysis of the role of different factors in the incidence trend can provide scientific basis and data support for the national health departments to formulate reasonable prevention and treatment policies.

Methods

The study collated the global burden disease study data of TC incidence from 1990 to 2019, and used APC model to analyze the contribution of age, period and birth cohort to the incidence trend of TC.

Results

There was an obvious unfavorable upward trend in terms of age and cohort effect all over the world. Since 2007, the growth rate of risk slowed down and the risk in female even decreased since 2012, which mainly contributed to the developed countries. In all SDI countries, 2002 is the dividing point of risk between male and female. In 2019, The global age-standardized incidence rate (ASIR) of TC in the 5 SDI countries all showed a significant upward trend, with the largest upward trend in the middle SDI countries.

Conclusion

The trend of rapid increase in the incidence of TC has begun to slow down, but the global incidence of TC has obvious gender and regional/national heterogeneity. Policy makers should tailor specific local strategies to the risk factors of each country to further reduce the burden of TC.

Radiomics in Oncological PET Imaging: A Systematic Review-Part 1, Supradiaphragmatic Cancers

Radiomics is an upcoming field in nuclear oncology, both promising and technically challenging. To summarize the already undertaken work on supradiaphragmatic neoplasia and assess its quality, we performed a literature search in the PubMed database up to 18 February 2022. Inclusion criteria were: studies based on human data; at least one specified tumor type; supradiaphragmatic malignancy; performing radiomics on PET imaging. Exclusion criteria were: studies only based on phantom or animal data; technical articles without a clinically oriented question; fewer than 30 patients in the training cohort. A review database containing PMID, year of publication, cancer type, and quality criteria (number of patients, retrospective or prospective nature, independent validation cohort) was constructed. A total of 220 studies met the inclusion criteria. Among them, 119 (54.1%) studies included more than 100 patients, 21 studies (9.5%) were based on prospectively acquired data, and 91 (41.4%) used an independent validation set. Most studies focused on prognostic and treatment response objectives. Because the textural parameters and methods employed are very different from one article to another, it is complicated to aggregate and compare articles. New contributions and radiomics guidelines tend to help improving quality of the reported studies over the years.