18F-Fluorocholine Positron Emission Tomography/Computed Tomography is a Highly Sensitive but Poorly Specific Tool for Identifying Malignancy in Thyroid Nodules with Indeterminate Cytology: The Chocolate Study

Significance of incidental thyroid 18F-fluorocholine uptake in patients with hyperparathyroidism imaged for localizing hyperfunctioning parathyroid glands

OBJECTIVE

18F-fluorocholine PET/CT is considered the imaging gold standard for detection of hyperfunctioning parathyroid glands . However, increased uptake might also occur in the thyroid gland. The aim of our study was to assess the incidence and significance of 18F-fluorocholine uptake in the thyroid gland in patients with hyperparathyroidism.

MATERIALS AND METHODS

This retrospective study includes 195 consecutive patients with hyperparathyroidism, who underwent 18F-fluorocholine PET/CT, for detection of hyperfunctioning parathyroid glands. PET/CT images were reviewed by two nuclear medicine physicians for the presence of focal or diffuse thyroid uptake. PET/CT results were compared with laboratory parameters, ultrasonography, EU-TIRADS classification in the presence of thyroid nodules, cytology, and final histology.

RESULTS

25 patients (13%) showed 18F-fluorocholine uptake in the thyroid gland: focal thyroid uptake (FTU) in 7 patients (4%), diffuse thyroid uptake (DTU) in 8 patients (4%), and combined uptake (FTU + DTU) in 10 patients (5%), with a total of 20 active thyroid nodules. There was no correlation between EU-TIRADS classification and PET parameters. One highly 18F-fluorocholine active thyroid nodule and one isoactive thyroid nodule turned out to be papillary thyroid cancers in the final histology; 50% of the patients with DTU had Hashimoto's thyroiditis.

CONCLUSION

Incidental 18F-fluorocholine uptake in the thyroid gland was observed in 13% of patients. As reported for 18F-FDG, focal 18F-fluorocholine uptake might represent thyroid cancer and should be evaluated with ultrasound and, if indicated, with fine-needle aspiration cytology. Diffuse 18F-fluorocholine uptake most likely represents multinodular goiter or Hashimoto's thyroiditis.

Differentiation of benign and malignant lesions in Bethesda III and IV thyroid nodules via dual-energy computed tomography quantitative parameters and morphologic features

Background

Thyroid nodules (TNs) cytologically defined as category Bethesda III and IV pose a major diagnostic challenge before surgery, demanding new methods to reduce unnecessary diagnostic thyroid lobectomies for patients with benign TNs. This study aimed to assess whether a model combining dual-energy computed tomography (DECT) quantitative parameters with morphologic features could reliably differentiate between benign and malignant lesions in Bethesda III and IV TNs.

Methods

Data from 77 patients scheduled for thyroid surgery for Bethesda III and IV TNs (malignant =48; benign =29) who underwent DECT scans were reviewed. DECT quantitative parameters including normalized iodine concentration (NIC), attenuation on the slope of spectral Hounsfield unit (HU) curve, and normalized effective atomic number (Zeff) were measured in the arterial phase (AP) and venous phase (VP). DECT quantitative parameters and morphologic features were compared between the malignant and benign cohorts. The receiver operating characteristic curve was performed to compare the performances of significant DECT quantitative parameters, morphologic features, or the models combining the DECT parameters, respectively, with morphologic features. A nomogram was constructed from the optimal performance model, and the performance was evaluated via the calibration curve and decision curve analysis.

Results

The areas under the receiver operating characteristic curve with 95% confidence interval (CI) of the NIC in the AP (AP-NIC), slope of spectral HU curve in the AP, and NZeff in the AP were 0.749 (95% CI: 0.641-0.857), 0.654 (95% CI: 0.530-0.778), and 0.722 (95% CI: 0.602-0.842), respectively. The model combining AP-NIC with enhanced blurring showed the highest diagnostic performance, with an area under the receiver operating characteristic curve (AUC), sensitivity, and specificity of 0.808, 0.854, and 0.655, respectively; it was then used to construct a nomogram. The calibration curve showed that the discrepancy between the prediction of the nomogram and actual observations was less than 5%. The decision curve analysis indicated the nomogram had a positive net benefit in threshold risk ranges of 14% to 58% or 60% to 91% for malignant Bethesda III and IV TNs.

Conclusions

The model combining AP-NIC with enhanced blurring could reliably differentiate between benign and malignant lesions in Bethesda III and IV TNs.

Cost-effectiveness of one-stop-shop [18F]Fluorocholine PET/CT to localise parathyroid adenomas in patients suffering from primary hyperparathyroidism

PURPOSE

We conducted a cost-effectiveness analysis in which we compared a preoperative [18F]Fluorocholine PET/CT-based one-stop-shop imaging strategy with current best practice in which [18F]Fluorocholine PET/CT is only recommended after negative or inconclusive [99mTc]Tc-methoxy isobutyl isonitrile SPECT/CT for patients suffering from primary hyperparathyroidism. We investigated whether the one-stop-shop strategy performs as well as current best practice but at lower costs.

METHODS

We developed a cohort-level state transition model to evaluate both imaging strategies respecting an intraoperative parathyroid hormone monitored treatment setting as well as a traditional treatment setting. The model reflects patients' hospital journeys after biochemically diagnosed primary hyperparathyroidism. A cycle length of twelve months and a lifetime horizon were used. We conducted probabilistic analyses simulating 50,000 cohorts to assess joint parameter uncertainty. The incremental net monetary benefit and cost for each quality-adjusted life year were estimated. Furthermore, threshold analyses regarding the tariff of [18F]Fluorocholine PET/CT and the sensitivity of [99mTc]Tc-methoxy isobutyl isonitrile SPECT/CT were performed.

RESULTS

The simulated long-term health effects and costs were similar for both imaging strategies. Accordingly, there was no incremental net monetary benefit and the one-stop-shop strategy did not result in lower costs. These results applied to both treatment settings. The threshold analysis indicated that a tariff of €885 for [18F]Fluorocholine PET/CT was required to be cost-effective compared to current best practice.

CONCLUSION

Both preoperative imaging strategies can be used interchangeably. Daily clinical practice grounds such as available local resources and patient preferences should inform policy-making on whether a hospital should implement the one-stop-shop imaging strategy.

Assessment of the risk of malignancy in Bethesda III thyroid nodules: a comprehensive review

The increasing prevalence of thyroid cancer emphasizes the need for a thorough assessment of risk of malignancy in Bethesda III nodules. Various methods ranging commercial platforms of molecular genetic testing (including Afirma® GEC, Afirma® GSC, ThyroSeq® V3, RosettaGX®, ThyGeNEXT®/ThyraMIR®, ThyroidPRINT®) to radionuclide scans and ultrasonography have been investigated to provide a more nuanced comprehension of risk estimation. The integration of molecular studies and imaging techniques into clinical practice may provide clinicians with improved and personalized risk assessment. This integrated approach we feel may enable clinicians to carefully tailor interventions, thereby minimizing the likelihood of unnecessary thyroid surgeries and overall crafting the optimal treatment. By aligning with the evolving landscape of personalized healthcare, this comprehensive strategy ensures a patient-centric approach to thyroid nodule and thyroid cancer management.

The role of 18F-fluoromethylcholine-positron emission tomography-computed tomography for preoperative localization of hyperfunctioning parathyroid glands with special emphasis on multiglandular disease: a retrospective cohort study

Background

Primary hyperparathyroidism (PHPT) is a common endocrine disorder. Definitive treatment is surgical. Preoperative localization of diseased glands increases the chance of successful treatment. The aim of this study is to investigate the diagnostic performance of 18F-fluoromethylcholine-positron emission tomography-computed tomography (18F-FCh-PET-CT) in preoperative localization of diseased parathyroid glands, when first-line examinations were inconclusive.

Methods

This is a retrospective study. All patients with PHPT who underwent 18F-FCh-PET-CT, after inconclusive ultrasound examination and 99mTc-methoxyisobutylisonitrile/single-photon emission CT-CT, were included in cohort I. Patients who were subsequently operated for their parathyroid disease, were included in cohort II. The performance of 18F-FCh-PET-CT was analyzed in two sets: per-lesion, and per-gland analysis.

Results

Out of 52 patients in cohort I, 18F-FCh-PET-CT identified single or multiple parathyroid lesions in 43 patients (83%). Nine patients had multiglandular disease. Thirty-four (65%) patients were subsequently operated and included in cohort II. Forty-four lesions were removed from these patients and 33 patients (97%) were cured. 18F-FCh-PET-CT localized 40 out of 44 lesions, with per-lesion and per-gland sensitivities of 97% and 95%, and positive predictive values (PPVs) of 93% and 87%, respectively, in addition to a specificity of 97% and a negative predictive value (NPV) of 94% in the per-gland analysis. Comparable excellent results were detected in multiglandular disease with sensitivity of 94.1%, specificity of 89%, PPV of 84%, and NPV of 94%.

Conclusions

Our study demonstrates the high diagnostic performance of 18F-FCh-PET-CT in the preoperative localization of diseased parathyroid gland in patients with PHPT, especially in multiglandular PHPT.

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.

18F-fluorocholine PET/CT semi-quantitative analysis in patients affected by primary hyperparathyroidism: a comparison between laboratory and functional data

INTRODUCTION

This retrospective study aims to establish ¹⁸F-fluorocholine (FCH) positron emission tomography/computed tomography (PET/CT) performance in finding hyperfunctioning parathyroid glands, analyze a potential role for semi-quantitative PET parameters and assess factors that may influence PET/CT outcome.

METHODS

Forty patients with suspect primary hyperparathyroidism (pHPT) and negative/equivocal conventional imaging underwent FCH-PET/CT in our Institution. For every lesion, visual and semi-quantitative analyses were performed on PET/CT images. In qualitative analysis, a lesion was considered positive if a clear focus of uptake, significantly higher than normal thyroid tissue, was identifiable. Ectopic focal uptake was also regarded as positive PET result. Lesion SUV_Max was measured by assigning a spheric VOI to the suspect area of uptake. Thyroid SUV_Mean was assessed by placing a spheric VOI inside the contralateral thyroid lobe, and SUV_ratio was calculated using this background region. All patients were subsequently submitted to surgery and histopathologic workup. Sensitivity, positive predictive value (PPV) and accuracy were calculated based on histopathologic reports for every lesion. Pearson's test was used to assess a correlation between laboratory and histopathologic features with SUVr.

RESULTS

Four out of the 40 patients who underwent surgery for pHPT had more than one histologic proven unhealthy parathyroid and three had papillary thyroid cancer (PTC). A total of 48 lesions were analyzed. We found 42/48 lesions (87.5%) to have true-positive uptake, whereas three lesions (6.7%) had false-positive uptake (PTC). Three histologic proven parathyroid adenomas showed no uptake (6.7%); the sensitivity/PPV were 93.3% and accuracy was 87,8%. Pearson's test showed a significant correlation between PTH values and parathyroid size with SUVr values (r = 0.56 and 0.55, respectively, p < 0.01 for both features).

DISCUSSION

As stated in recent literature, we observed excellent diagnostic sensitivity of FCH-PET/CT in patients with pHPT, providing surgeons a fine tool to optimize treatment. More studies are needed to improve the evaluability of semi-quantitative parameters towards a further improvement of diagnostic accuracy.

SFE-AFCE-SFMN 2022 Consensus on the management of thyroid nodules : What is the role of functional imaging and isotopic treatment?

The SFE-AFCE-SFMN 2022 consensus deals with the management of thyroid nodules, a condition that is a frequent reason for consultation in endocrinology. In more than 90% of cases, patients are euthyroid, with benign non-progressive nodules that do not warrant specific treatment. The clinician's objective is to detect malignant thyroid nodules at risk of recurrence and death, toxic nodules responsible for hyperthyroidism or compressive nodules warranting treatment. The diagnosis and treatment of thyroid nodules requires close collaboration between endocrinologists, nuclear medicine physicians and surgeons, but also involves other specialists. Therefore, this consensus statement was established jointly by 3 societies: the French Society of Endocrinology (SFE), French Association of Endocrine Surgery (AFCE) and French Society of Nuclear Medicine (SFMN); the various working groups included experts from other specialties (pathologists, radiologists, pediatricians, biologists, etc.). This section deals with the role of thyroid scintigraphy in the diagnosis of autonomous thyroid nodules, nuclear medicine in nodules with indeterminate cytology and iodine treatment for autonomous thyroid nodules.

Thyroid 18F-fluorocholine uptake in patients with chronic autoimmune thyroiditis

Objective

18F-Fluorocholine (18FCH) PET/CT has high sensitivity for parathyroid adenoma detection and can reliably exclude malignancy in thyroid nodules with indeterminate cytology. Data regarding 18FCH uptake in chronic autoimmune thyroiditis (CAT) are scarce. We aimed to assess thyroid 18FCH uptake in CAT with biological and histological correlation.

Methods

This is an ancillary study from the Chocolate trial (NCT02784223) that prospectively enrolled 107 patients planned for thyroid surgery. 18FCH PET/CT acquisitions were performed 20 and 60 min after injection. 18FCH uptake in the thyroid gland was assessed by measuring maximum (SUVmax) and mean (SUVmean) standardized uptake values. Thyrotropin, free thyroxine (FT4), thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies were collected. The intensity of thyroiditis and the degree of fibrosis were assessed on pathology.

Results

CAT was evidenced in 19/107 (18%) patients. Of these, 13 (68%) displayed an increased and diffuse 18FCH thyroid uptake. This uptake pattern was not observed in patients without CAT. SUVmax and SUVmean were higher in patients with CAT than in those without (P < 0.001). At both acquisition times, SUVmax showed a monotonic relationship with the intensity of thyroiditis (Spearman ρ = 0.44 and 0.51, respectively, P < 0.001) and with the degree of fibrosis (Spearman ρ = 0.55 and 0.62, respectively, P < 0.001). SUVmax showed a linear relationship with TPOAb titers at 20 min (Pearson r = 0.54, P < 0.05; Spearman ρ = 0.59, P = 0.03).

Conclusions

More than two-thirds of the patients with CAT present high and diffuse thyroid 18FCH uptake. This uptake pattern is highly specific to CAT and is correlated with pathology and TPOAb titers.