Value of 18F-FDG PET negativity and Tg suppressibility as markers of prognosis in patients with elevated Tg and 131I-negative differentiated thyroid carcinoma (TENIS syndrome)

The impact of qualitative [18F]FDG PET/CT in predicting clinical outcomes of post-surgical differentiated thyroid cancer patients with elevated thyroglobulin and negative radioiodine whole-body scan

BACKGROUND

[18F]FDG PET/CT has been widely used as a diagnostic tool in detection and localization of recurrent non-avid radioiodine lesions in post-operative differentiated thyroid cancer (DTC) patients with elevated serum thyroglobulin but negative radioiodine whole-body scan (TENIS) syndrome. The aim of our study was to evaluate the role of [18F]FDG PET/CT in prediction on outcomes of these DTC patients.

METHODS

Post-operative DTC patients with TENIS syndrome were collected in the department of nuclear medicine, Hospital 108 from 2019 to 2023. Patients underwent [18F]FDG PET/CT with standard protocol following EANM guideline for tumor imaging version 2.0. The qualitative [18F]FDG PET/CT imaging characteristics were classified into three categories: (i) negative [18F]FDG PET/CT, (ii) minimal [18F]FDG PET/CT volume of lesions, (iii) extensive [18F]FDG PET/CT volume of lesions. Progression-free survival (PFS) and overall survival (OS) were the end point of the study. The prognosis of qualitative [18F]FDG PET/CT in predicting PFS and OS was illustrated by Kaplan-Meier survival analysis. The independent factors predicting PFS and OS were determined by univariate and multivariate analysis using logistic regression.

RESULTS

There were 164 consecutive patients, 51.2% female and 48.8% female. The most common histopathological type was papillary accounting for 91.5%. The median time of follow-up was 33.3 months, (range 6.57 - 82.5). There was 70 (36.6%) progressions and 12 (7.35%) deaths. Negative [18F]FDG PET/CT uptake patients had median PFS with median 57.1 months which was higher than that of minimal category (46.2 months), and extensive category (37.6 months) (p < 0,001). 1-year OS and 5-year OS in extensive PET/CT category was 97.8% and 86.2% respectively which were significantly lower than that of negative and minimal categories (p = 0.053). In multivariate analysis, age at the time of diagnosis, pulmonary, bone metastases and extensive [18F]FDG PET/CT volume of lesions were the independent factor predicting PFS. Bone metastasis was only the factor could predict OS in multivariate analysis.

CONCLUSIONS

The minimal and negative [18F]FDG PET/CT categories had better prognosis than extensive category in PFS and OS. Extensive [18F]FDG PET/CT category was an independent factor for predicting PFS. Bone metastasis was only the independent factor that could predict both PFS and OS.

Match Point: Nuclear Medicine Imaging for Recurrent Thyroid Cancer in TENIS Syndrome-Systematic Review and Meta-Analysis

Background/Objectives: Disease recurrence and resistance to radioiodine (RAI) therapy are major challenges in the management of differentiated thyroid cancer (DTC). In particular, the TENIS (Thyroglobulin Elevated Negative Iodine Scintigraphy) syndrome, characterised by elevated thyroglobulin (Tg) serum levels in addition to a negative radioiodine whole body scan (WBS), complicates disease monitoring and treatment decisions. Conventional imaging techniques often fail to detect disease in WBS-negative patients with rising Tg levels, leading to limitations in therapeutic intervention. This systematic review and meta-analysis aims to evaluate the diagnostic accuracy of nuclear imaging modalities in detecting disease recurrence in patients with the TENIS syndrome and to provide insights to guide therapeutic approaches in this complex clinical scenario. Methods: A comprehensive search of PubMed/MEDLINE and EMBASE databases up to March 2024 was performed according to PRISMA guidelines. Eligible studies were selected, and quality assessment was performed with the QUADAS-2 tool. For each study, relevant data were extracted and synthesised. A meta-analysis of the diagnostic accuracy of [18F]FDG PET/CT was performed, and patient-based pooled sensitivity and specificity were calculated using a random-effects model. Statistical heterogeneity between studies was assessed using the I2 statistic. Results: Of the 538 studies initially identified, 22 were included in the systematic review, of which 18 were eligible for meta-analysis. The eligible studies, mainly focused on [18F]FDG PET/CT, showed variable sensitivity and specificity for the detection of RAI-refractory thyroid cancer lesions. For [18F]FDG PET/CT, pooled estimates displayed a sensitivity of 0.87 (95% CI: 0.82-0.90) and a specificity of 0.76 (95% CI: 0.61-0.86), with moderate heterogeneity between studies. Conclusions: [18F]FDG PET/CT remains central in the detection of disease recurrence in patients with the TENIS syndrome. The emergence of novel radiopharmaceuticals with specific molecular targets is a promising way to overcome the limitations of [18F]FDG in these patients and to open new theranostics perspectives. This review highlights the great potential of nuclear medicine in guiding therapeutic strategies for RAI-refractory thyroid cancer.

Assessment of Pulmonary Metastasis in Differentiated Thyroid Carcinoma: Value of HRCT Correlation with Functional Imaging

Pulmonary metastases in thyroid carcinoma demonstrates varying imaging characteristics and disease biology and the outcome. The valuable complimentary role of high-resolution CT (HRCT) in conjunction with functional imaging such as radioiodine scan has been discussed and illustrated in this review along with the varied clinical and imaging presentations of lung metastases from differentiated thyroid cancer (DTC). A multi-modality patient-specific diagnostic approach and awareness about the atypical presentations helps in early identification as well as effective management of these patients, and especially in certain situations that could need multi-disciplinary management. While HRCT of the lungs as an added tool provides detailed visualization of the lung parenchyma, in the era of hybrid imaging, the routine adoption of SPECT-CT in patients with pulmonary metastases (in diagnostic or post-treatment settings) could provide equivalent or even incremental information from further management viewpoint.

Tenosynovial Giant Cell Tumor of Foot in a Patient with Radioiodine-Refractory Thyroid Cancer: Imaging Findings on FDG-PET/CT, MRI, and Radioiodine Scan

We herein illustrate a case of benign tenosynovial giant cell tumor, which was incidentally detected as FDG-avid lesion on PET/CT in a patient with radioiodine refractory thyroid cancer, with predominantly non-iodine concentrating disease. The lesion was followed up clinically and with local MRI annually for subsequent 3 years. The utility of hybrid PET-CT imaging, the non-iodine concentration of the tumor along with clinical knowledge, and findings on other imaging and pathological modalities in answering and diagnosing incidental benign musculoskeletal tumors in a patient with known thyroid malignancy are presented here.

Impact of FDG-PET on therapy management and outcome of differentiated thyroid carcinoma patients with elevated thyroglobulin despite negative iodine scintigraphy

AIM

 The objective of this study was to assess the impact of implementing FDG-PET imaging in treatment algorithms for differentiated thyroid cancer with suspected recurrence. Primary end points were overall, event-free and disease-specific survival. Secondary end points were therapies, disease control and the sensitivity and specificity of PET imaging.

METHODS

 194 patients with DTC treated at our center from 1996 to 2014 following thyroidectomy and routine 131I ablation with no remaining 131I uptake in whole-body scans but persisting or rising thyroglobulin values were enrolled in this retrospective analysis. Of these, 149 (76.8 %) received an 18F-FDG scan (PET group) whereas the remaining 45 patients (23.2 %) did not (non-PET group). Survival, disease-specific characteristics at inclusion, disease control and therapies were compared.

RESULTS

 Patients of the PET group generally showed characteristics associated with higher disease activity from inclusion onwards. This did not translate to statistically significant differences in survival. If PET imaging was performed following inclusion, patients received significantly less radioiodine treatments during the first nine months after inclusion (63.1 % of the PET-group vs 82.2 % of the non-PET group). Simultaneously, patients tended to receive more surgeries following PET imaging (27.5 % PET-group vs 13.3 % non-PET group). No significant differences regarding disease control were observed.

CONCLUSION

 The early use of FDG-PET imaging in cases of suspected recurrence or existence of dedifferentiated DTC can lead to changes in therapy management, specifically identifying patients unlikely to benefit from additional radioiodine therapy who would instead qualify for surgical therapy methods.

Designing and Developing PET-Based Precision Model in Thyroid Carcinoma: The Potential Avenues for a Personalized Clinical Care

This communication enumerates the current uses and potential areas where PET could be clinically utilized for developing "precision medicine" type model in thyroid carcinoma. (1) In routine clinics, PET imaging (with fluorodeoxyglucose [FDG]) is utilized to investigate patients of differentiated thyroid carcinoma (DTC) with high thyroglobulin and negative iodine scintigraphy (TENIS) and in medullary carcinoma thyroid (MCT) when the tumor markers (eg, calcitonin and carcino embryonic antigen [CEA]) are raised postoperatively (PET with FDG, ⁶⁸Ga-DOTA-NOC/TATE, FDOPA). Both are examples of management personalization, where PET-computed tomography (CT) has been found substantially useful in detecting sites of metastatic disease and making decision with regard to feasibility and planning of surgery on an individual patient basis. (2) The next important area of management personalization is in patients of TENIS with metastatic disease not amenable to surgery through examining FDG-PET findings in tandem with radio iodine scan and ⁶⁸Ga-DOTA-TATE/NOC PET/CT. Heterogeneous behavior of the metastatic lesions is frequently observed clinically: analyzing the findings of three studies aids in sub-segmenting patients into subgroups and thereby deciding upon the best approach (observation with LT4 suppression vs PRRT vs tyrosine kinase inhibitors) that could be individualized in a given case. (3) In metastatic/inoperable MCT, ⁶⁸Ga-DOTA-TATE/NOC PET-CT helps in deciding upon feasibility of targeted PRRT in an individual patient and helps in follow-up and response evaluation. (4) Disease prognostification with FDG-PET is evolving both in DTC and MCT, where FDG avidity would indicate an aggressive biology, though the implication of this from treatment viewpoint is unclear at this point. Conversely, a negative FDG-PET in DTC and TENIS would suggest a favorable prognosis in an individual. (5) Iodine-124 PET/CT has the added potential of obtaining lesional dosimetry compared to the SPECT approach, and could help in selecting appropriate doses on an individual basis.

Assessment of the Role of Different Imaging Modalities with Emphasis on Fdg Pet/Ct in the Management of Well Differentiated Thyroid Cancer (WDTC)

BACKGROUND

Positron emission tomography/computed tomography is suggested to have a role in detection of iodine negative recurrence in well differentiated thyroid cancer. The aim of this study is to identify role of different imaging modalities in the management of well differentiated thyroid cancer.

METHODS

We reviewed 900 well differentiated thyroid cancer patients after post-thyroidectomy who underwent recombinant human thyroid stimulating hormone stimulated Sodium Iodide I 131 imaging. Out of 900 patients, 74 had positron emission tomography/computed tomography. Multivariate analysis was performed by controlling positron emission tomography/computed tomography, Sodium Iodide I 131 scan, neck ultrasonography, age, sex, primary tumor size, stage, histology, thyroglobulin. Patients were grouped according to results of Sodium Iodide I 131 scan and positron emission tomography/computed tomography.

RESULTS

Positron emission tomography/computed tomography was positive in 23 of 74 patients. The sensitivity for positron emission tomography was 11/11(100%), the specificity was 51/63 (81.0%), the positive predictive value was 11/23 (47.8%), and the negative predictive value was 51/51 (100%). The sensitivity for the neck ultrasonography was 4/8 (50%), the specificity was 53/60 (88.3%), positive predictive value was 4/11 (36.4%), and negative predictive value was 53/57 (93.0%). 50% of patients who had Sodium Iodide I 131 negative scan and positive positron emission tomography/computed tomography had a change in management. Thirty-six percent with positive neck ultrasonography had a change in management. Out of 11 recurrences, 6 had distant metastatic disease, and 5/11 had regional nodal disease. Neck ultrasonography showed nodal metastasis in 4/5 (80%).

CONCLUSION

Positron emission tomography/computed tomography altered management in the presence of a high thyroglobulin level and a negative Sodium Iodide I 131 scan. Neck ultrasonography should be the first line of imaging with rising thyroglobulin levels. Positron emission tomography/computed tomography should be considered for cases with high thyroglobulin levels and normal neck ultrasonography to look for distant metastatic disease.