Defining a rational step-care algorithm for managing thyroid carcinoma patients with elevated thyroglobulin and negative on radioiodine scintigraphy (TENIS): considerations and challenges towards developing an appropriate roadmap

Radiolabeled Somatostatin Analogs for Cancer Imaging

Somatostatin receptors (SSTR) are expressed by many tumours especially those related to neuro-endocrine origin and molecular functional imaging of SSTR expression using radiolabelled somatostatin analogs have revolutionized imaging of patients with these group of malignancies. Coming a long way from the first radiolabelled somatostatin analog 123I-Tyr-3-octreotide, there has been significant developments in terms of radionuclides used, the ligands and somatostatin derivatives. 111In-Pentetreotide extensively employed for imaging NETs at the beginning has now been replaced by 68Ga-SSA based PET-CT. SSA-PET/CT performs superior to conventional imaging modalities and has evolved in the mainframe for NET imaging. The advantages were multiple: (i) superior spatial resolution of PET versus SPECT, (ii) quantitative capabilities of PET aiding in disease activity and treatment response monitoring with better precision, (iii) shorter scan time and (iv) less patient exposure to radiation. The modality is indicated for staging, detecting the primary in CUP-NETs, restaging, treatment planning (along with FDG: the concept of dual-tracer PET-CT) as well as treatment response evaluation and follow-up of NETs. SSA PET/CT has also been incorporated in the guidelines for imaging of Pheochromocytoma-Paraganglioma, Medullary carcinoma thyroid, Meningioma and Tumor induced osteomalacia. At present, there is rising interest on (a) 18F-labelled SSA, (b) 64Cu-labelled SSA, and (c) somatostatin antagonists. 18F offers excellent imaging properties, 64Cu makes delayed imaging feasible which has implications in dosimetry and SSTR antagonists bind with the SST receptors with high affinity and specificity, providing high contrast images with less background, which can be translated to theranostics effectively. SSTR have been demonstrated in non-neuroendocrine tumours as well in the peer-reviewed literature, with studies demonstrating the potential of SSA PET/CT in Neuroblastoma, Nasopharyngeal carcinoma, carcinoma prostate (neuroendocrine differentiation) and lymphoma. This review will focus on the currently available SSAs and their history, different SPECT/PET agents, SSTR antagonists, comparison between the various imaging tracers, and their utility in both neuroendocrine and non-neuroendocrine tumors.

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.

Comprehensive Review of the Imaging Recommendations for Diagnosis, Staging, and Management of Thyroid Carcinoma

Thyroid cancer is the most common head and neck cancer (HNC) in the world. In this article, we comprehensively cover baseline, posttreatment, and follow-up imaging recommendations for thyroid carcinomas along with the eighth edition of the tumor, node, metastasis (TNM) staging system proposed by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC). We include characterization and risk stratification of thyroid nodules on ultrasound (US) proposed by various international bodies. Management guidelines (depending upon the type of thyroid carcinoma) based on the international consensus recommendations (mainly by the American Thyroid Association) are also extensively covered in this article, including the role of a radioiodine scan. The management of recurrent disease is also briefly elucidated in this article. In addition, we cover the risk factors and etiopathogenesis of thyroid carcinoma along with the non-imaging diagnostic workup essential for thyroid carcinoma management, including the significance of genetic mutations. US is the diagnostic imaging modality of choice, with US-guided fine needle aspiration (FNA) being the procedure of choice for tissue diagnosis. The roles of computed tomography (CT), magnetic resonance imaging (MRI), and fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT) in thyroid carcinoma staging are also specified. Through this article, we aim to provide a comprehensive reference guide for the radiologists and the clinicians in the pursuit of optimal care for patients with thyroid carcinoma.

Prospective evaluation of 68 Ga-NODAGA-RGD PET-CT in patients of carcinoma thyroid with thyroglobulin elevated negative radioiodine scintigraphy (TENIS) with a head-to-head comparison with FDG-PET/CT

BACKGROUND AND AIM

This study aimed to examine the expression of RGD binding integrins in patients of elevated serum thyroglobulin (Tg) level with negative radioiodine scintigraphy (TENIS) employing 68 Ga-NODAGA-RGD PET-CT.

MATERIAL AND METHODS

This was a prospective study involving 30 proven cases of TENIS with histopathological diagnosis of differentiated thyroid carcinoma post-surgery. In addition to observing the lesional concentration on 68 Ga-NODAGA-RGD PET-CT, a 4-point visual grading system (grade I-IV), was undertaken to estimate the degree of radiotracer avidity, for potential of theranostics.

RESULTS

On 18 F-FDG-PET/CT, the uptake was seen in 182 lesions out of a total of 200 (91%). 68 Ga-NODAGA-RGD PET-CT showed expression in a total of 110/200 (55%) lesions. On patient-specific analysis, 68 Ga-NODAGA-RGD PET-CT was positive for the disease in 21/30 patients (70%) and negative in 9/30 (30%) patients. The overall patient-specific sensitivity and specificity of 68 Ga-NODAGA-RGDPET-CT were 75% and 100%, respectively. 18 F-FDG PET-CT was positive for the disease in 26/30 patients (86.66%) and negative in 4/30 (13.33%) patients. The overall patient-specific sensitivity and specificity of 18 F-FDG-PET/CT were 92.86% and 100%, respectively. The 4-point visual grading system revealed 14/200 (7%) lesions demonstrating Grade I uptake, 49/200 (24.5%) lesions grade II uptake, 17/200 (8.5%) lesions grade III uptake and 40/200 (20%) lesions grade IV uptake.

CONCLUSION

The results suggested that RGD-binding integrin is expressed in a sizeable fraction of metastatic lesions of TENIS cases, albeit demonstrating a varying degree of uptake. Out of the soft tissue, lung, and bone lesions, metastatic bone lesions showed more RGD affinity than other sites. The patients with substantial RGD uptake on a 4-point visual grading system may be potential targets for RGD-based therapy.

Tata Memorial Centre Evidence Based Use of Nuclear medicine diagnostic and treatment modalities in cancer

ABSTRACT

PET/CT and radioisotope therapy are diagnostic and therapeutic arms of Nuclear Medicine, respectively. With the emergence of better technology, PET/CT has become an accessible modality. Diagnostic tracers exploring disease-specific targets has led the clinicians to look beyond FDG PET. Moreover, with the emergence of theranostic pairs of radiopharmaceuticals, radioisotope therapy is gradually making it's way into treatment algorithm of common cancers in India. We therefore would like to discuss in detail the updates in PET/CT imaging and radionuclide therapy and generate a consensus-driven evidence based document which would guide the practitioners of Oncology.

The Diagnostic Value of 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Differentiated Thyroid Cancer Patients with Elevated Thyroglobulin/Thyroglobulin Antibody Levels and Negative Iodine Scintigraphy: A Systematic Review and Meta-Analysis

Background: The objective of this study is to evaluate the diagnostic accuracy of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in detecting recurrence in patients with differentiated thyroid cancer (DTC) who have negative whole-body scans (WBSs) but elevated serum thyroglobulin (Tg) or thyroglobulin antibody (TgAb) levels. Methods: This systematic review/meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis for Diagnostic Test Accuracy criteria (International Prospective Register of Systematic Reviews registration number: CRD42022340924). A comprehensive search of the MEDLINE, EMBASE, and Cochrane databases identified articles reporting the diagnostic accuracy of FDG PET/CT for the detection of recurrence in patients with DTC with negative WBS and elevated serum Tg or TgAb levels published between January 2012 and June 2023. Meta-analyses were performed to determine the diagnostic accuracy of FDG PET/CT on the total target population as well as on subgroups stratified by serum Tg or TgAb, and thyrotropin (TSH) stimulation status at the time of FDG PET/CT. The Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) framework was applied to evaluate the quality of evidence and the strength of recommendations to facilitate translation of the meta-analysis results into practical recommendations for clinical guidelines. Results: A total of 24 studies involving 1988 patients were included for analysis. The overall pooled sensitivity and specificity values were 0.87 (95% confidence interval [CI] = 0.83-0.92; I2 = 75%) and 0.84 (CI = 0.80-0.89; I2 = 44%), respectively. Subgroup analyses revealed no significant differences in the diagnostic accuracy of FDG PET/CT in patients stratified by serum Tg or TgAb levels, and TSH stimulation status at the time of PET/CT. Treatment plans were changed following FDG PET/CT imaging in 40% (CI = 34-47%; I2 = 39%) of cases. The quality level of evidence for using FDG PET/CT was moderate in both sensitivity and specificity according to the GRADE system. Conclusion: There is moderate quality evidence demonstrating the high diagnostic accuracy of FDG PET/CT in detecting recurrence in patients with DTC with negative WBS and elevated serum Tg or TgAb levels. This evidence corroborates the current guidelines' endorsement of FDG PET/CT as a diagnostic tool in such patients.

Outcome of patients with differentiated thyroid cancer treated with empirical radioiodine therapy on the basis of Thyroglobulin Elevation Negative Iodine Scintigraphy (TENIS) syndrome without structural disease: a retrospective cohort study

BACKGROUND

For differentiated thyroid cancer (DTC) patients with thyroglobulin (Tg) elevation and negative iodine scintigraphy (commonly termed "TENIS" syndrome) after thyroidectomy, radioactive iodine (RAI) therapy, and thyroid-stimulating hormone (TSH) suppression therapy, empirical RAI therapy may be considered. However, the outcome data of TENIS syndrome without structural disease after empirical RAI therapy have not shown clear evidence of improvement in survival. We assessed the efficacy of such empirical RAI therapy in TENIS syndrome without structural disease and evaluated the progression-free survival (PFS).

METHODS

A total of 80 papillary thyroid cancer (PTC) patients with TENIS syndrome without structural disease were included in this retrospective study. 52 patients were treated with empirical RAI therapy while another 28 patients were untreated. The progression-free survival (PFS) of both groups was defined as the main outcome. The secondary outcome was the comparison of serum Tg levels 12 months after being diagnosed as TENIS syndrome.

RESULTS

The PFS of the empirical RAI therapy group was better than the untreated group (p < 0.001). Moreover, there was significant difference in Tg normalization between patients treated with empirical therapy and without treatment (p = 0.001). Empirical RAI therapy (p = 0.001) predicts better PFS. Male gender (p = 0.041) and empirical RAI therapy (p = 0.002) predict better remission in serum Tg level.

CONCLUSION

Patients with TENIS syndrome without structural disease can benefit from empirical RAI therapy in both PFS and Tg normalization.

An Appraisal and Update of Fluorodeoxyglucose and Non-Fluorodeoxyglucose-PET Tracers in Thyroid and Non-Thyroid Endocrine Neoplasms

Endocrine neoplasms and malignancies are a diverse group of tumors with varied clinical, histopathologic, and functional features. These tumors vary from sporadic to hereditary, isolated entities to multiple neoplastic syndromes, functioning and non functioning tumors, unifocal locally invasive, and advanced to multifocal tumors with disseminated distant metastases. The presence of various specific biomarkers and specific receptor targets serves as valuable tools for diagnosis, prognosis, and management. PET-CT with FDG and a multitude of novel and specific radiotracers towards specific therapeutic targets mandates personalization of their use, so as to ensure maximum clinical benefit in the management of these neoplasms.

MS. Changing Paradigm in Treatment of Differentiated Thyroid Cancer

Differentiated thyroid cancer is an indolent cancer with an excellent prognosis when treated adequately. The treatment algorithm is well established and standardized. Surgery followed by radio-iodine treatment has stood the test of time. In the last decade, the paradigm has slightly shifted with newer diagnostic approaches like stimulated thyroglobulin and anti-thyroglobulin antibodies impacting the treatment decisions. The diagnostic whole body radio-iodine scan has also got innovated with the introduction of r-TSH injection protocol wherein the scan is performed while the patient is on thyroxine thereby minimizing patient discomfort. The new RISK-based classification system has resulted in altered treatment algorithms by sub dividing patients into low-, intermediate-, and high-risk groups. There has also been identification of TWO new class of thyroid cancer patients-radio-iodine-resistant thyroid cancer and TENIS syndrome (thyroglobulin elevated negative iodine scan) patients. Both these groups posed major challenge to treatment and this resulted in incorporation of TARGETED THERAPY based on the mutations that occur in these TWO groups of patients. The introduction of Sorafenib and Lenvatinib has made significant impact on progression-free and overall survival of these patients. The introduction of THYROPET (124-I PET scan) is gaining momentum as an alternative to 123/131-I scans due to high-resolution images on PET scan increasing the detection sensitivity. All the above factors have resulted in paradigm shift in the management of differentiated thyroid cancer patients.

Papillary Thyroid Carcinoma in Ectopic Thyroid Tissue Within a Suspected Cervical Paraganglioma

ABSTRACT

Ectopic differentiated thyroid carcinoma represents less than 1% of all thyroid carcinoma cases, which usually arises along the cervical midline, and (delving into literature) there are scarce reports of such entity in nuclear medicine imaging studies. We present a rare case of a confirmed synchronous, orthotopic, and heterotopic (in lateral ectopic thyroid tissue) differentiated thyroid carcinoma in a patient who was previously misdiagnosed as having a cervical paraganglioma, based on compatible clinical, analytical, and imagenological (both structural and functional) findings.

Early Predictive Response to Multi-Tyrosine Kinase Inhibitors in Advanced Refractory Radioactive-Iodine Differentiated Thyroid Cancer: A New Challenge for [18F]FDG PET/CT

Differentiated thyroid cancer (DTC) represents the most common thyroid cancer histotype. Generally, it exhibits a good prognosis after conventional treatments; nevertheless, about 20% of patients can develop a local recurrence and/or distant metastasis. In one-third of advanced DTC, the metastatic lesions lose the ability to take up iodine and become radioactive iodine-refractory (RAI-R) DTC. In this set of patients, the possibility to perform localized treatments should always be taken into consideration before the initiation of systemic therapy. In the last decade, some multi-tyrosine kinase inhibitor (MKI) drugs were approved for advanced DTC, impacting on patient’s survival rate, but at the same time, these therapies have been associated with several adverse events. In this clinical context, the role of 2-deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography/computed tomography ([¹⁸F]FDG PET/CT) in the early treatment response to these innovative therapies was investigated, in order to assess the potentiality of this diagnostic tool in the early recognition of non-responders, avoiding unnecessary therapy. Herein, we aimed to present a critical overview about the reliability of [¹⁸F]FDG PET/CT in the early predictive response to MKIs in advanced differentiated thyroid cancer.

Production, characterization and in-vitro applications of single-domain antibody against thyroglobulin selected from novel T7 phage display library

Single- domain antibodies (SdAbs) have been deployed in various biomedical applications in the recent past. However, there are no reports of their use in the immunoradiometric assays (IRMA) for thyroglobulin (Tg). Tg is the precursor molecule for the biosynthesis of thyroid hormones: thyroxine and triiodothyronine, which are essential for the regulation of normal metabolism in all vertebrates. Patients with differentiated thyroid cancer (DTC) require periodic monitoring of their serum thyroglobulin levels, as it serves as a prognostic marker for DTC. Here, we report a methodology to produce SdAbs against human-Tg, by a hybrid immunization/directed-evolution approach by displaying the SdAb gene-repertoire derived from a hyperimmune camel in the T7 phage display system. We have demonstrated the immunoreactivity of anti-Tg-SdAb (KT75) in immunoassays for thyroglobulin and measured its affinity by surface plasmon resonance (K_D ~ 18 picomolar). Additionally, we have shown the quantitative-binding property of SdAb for the first time in IRMA for thyroglobulin. The serum Tg values obtained from SdAb-Tg-IRMA and in-house assay using murine anti-Tg-monoclonal antibody as tracer significantly correlated, r = 0.81, p < 0.05. Our results highlight the scope of using the T7 phage display system as an alternative for the conventional M13-phage to construct single-domain antibody display libraries.

Incremental diagnostic value of [18F]tetrafluoroborate PET-CT compared to [131I]iodine scintigraphy in recurrent differentiated thyroid cancer

INTRODUCTION

Efficient therapy of recurrent differentiated thyroid cancer (DTC) is dependent on precise molecular imaging techniques targeting the human sodium iodide symporter (hNIS), which is a marker both of thyroid and DTC cells. Various iodine isotopes have been utilized for detecting DTC; however, these come with unfavorable radiation exposure and image quality ([131I]iodine) or limited availability ([124I]iodine). In contrast, [18F]tetrafluoroborate (TFB) is a novel radiolabeled PET substrate of hNIS, results in PET images with high-quality and low radiation doses, and should therefore be suited for imaging of DTC. The aim of the present study was to compare the diagnostic performance of [18F]TFB-PET to the clinical reference standard [131I]iodine scintigraphy in patients with recurrent DTC.

METHODS

Twenty-five patients with recurrent DTC were included in this retrospective analysis. All patients underwent [18F]TFB-PET combined with either CT or MRI due to newly discovered elevated TG levels, antiTG levels, sonographically suspicious cervical lymph nodes, or combinations of these findings. Correlative [131I]iodine whole-body scintigraphy (dxWBS) including SPECT-CT was present for all patients; correlative [18F]FDG-PET-CT was present for 21 patients. Histological verification of [18F]TFB positive findings was available in 4 patients.

RESULTS

[18F]TFB-PET detected local recurrence or metastases of DTC in significantly more patients than conventional [131I]iodine dxWBS and SPECT-CT (13/25 = 52% vs. 3/25 = 12%, p = 0.002). The diagnosis of 6 patients with cervical lymph node metastases that showed mildly increased FDG metabolism but negative [131I]iodine scintigraphy was changed: [18F]TFB-PET revealed hNIS expression in the metastases, which were therefore reclassified as only partly de-differentiated (histological confirmation present in two patients). Highest sensitivity for detecting recurrent DTC had the combination of [18F]TFB-PET-CT/MRI with [18F]FDG-PET-CT (64%).

CONCLUSION

In the present cohort, [18F]TFB-PET shows higher sensitivity and accuracy than [131I]iodine WBS and SPECT-CT in detecting recurrent DTC. The combination of [18F]TFB-PET with [18F]FDG-PET-CT seems a reasonable strategy to characterize DTC tumor manifestations with respect to their differentiation and thereby also individually plan and monitor treatment. Future prospective studies evaluating the potential of [18F]TFB-PET in recurrent DTC are warranted.

Hyperplastic thymus with increased angiogenesis is correlated with elevated serum thyroglobulin level in differentiated thyroid cancer patients with TENIS syndrome

Aims

To investigate the association between angiogenetic activity of hyperplastic thymus and serum thyroglobulin (Tg) level in differentiated thyroid carcinoma patients with thyroglobulin (Tg)-elevated Negative Iodine Scintigraphy (TENIS) Syndrome.

Methods

A cohort of 30 consecutive patients who underwent total thyroidectomy followed by radioiodine ablation and had TENIS syndrome received integrin α_vβ₃ targeted imaging with ^99mTc-HYNIC-PEG4-E[PEG4-c(RGDfk)]2 (^99mTc-3PRGD2). The correlation of angiogenetic activity of the thymus and the serum Tg levels was evaluated in patients with enlarged thymus.

Results

Enlarged thymus was detected in 9 out of the 30 TENIS patients and all hyperplastic thymus showed an increased accumulation of the tracer (median tumor/background ratio: 2.8). Five of them had only mediastinal uptake and surgical removal of the mediastinal mass in one provided histopathologic evidence of thymic tissue. The other four were not assigned further treatment and were free of disease in the follow-up, though their stimulated Tg levels consistently increased. Four out of the 9 patients showed ^99mTc-3PRGD2 uptake outside the mediastinum were assigned surgery followed by radioiodine treatment. Their stimulated Tg levels decreased after iodine ablation, but not drop back to normal. A significant linear correlation was observed between serum Tg levels and the degree of angiogenesis in the hyperplastic thymus.

Conclusions

The angiogenetic activity in hyperplastic thymus was related with the consistently elevated serum Tg levels in TENIS syndrome patients. Based on the existing literature and current data, we propose further intervention for patients with RGD uptake outside thymus, while close follow-up for patients with only mediastinal uptake.

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.

68Ga DOTATATE PET/CT in Differentiated Thyroid Carcinoma With Fibular Metastasis and Mixed Response to Sorafenib

We describe somatostatin receptor targeted imaging findings in a 56-year-old woman with elevated serum thyroglobulin and radioiodine negative DTC fibular metastasis. The fibular lesion was biopsy proven of poorly differentiated thyroid carcinoma and demonstrated high grade uptake on Tc-HYNIC-TOC scintigraphy. She opted for sorafenib therapy for progressively increasing fibular swelling and was started on 400 mg daily followed by dose escalation to 400 mg twice daily. At 17 months after sorafenib initiation, Ga DOTATATE PET/CT demonstrated necrosis of the fibular lesion; however, new lesions were documented in lower dorsal and lumbar vertebrae and skull, based upon which sorafenib withdrawal was contemplated.

Grouping of Metastatic Thyroid Carcinoma by Molecular Imaging Features to Allow for Individualized Treatment, with Emphasis on the TENIS Syndrome

The process of radioiodine ((131)I) refractoriness, dedifferentiation, and development of thyroglobulin elevation and negative iodine scintigraphy (TENIS) syndrome in metastatic differentiated thyroid carcinoma (DTC) could be viewed as a disease continuum rather than a single event or an all-or-none phenomenon. In this report, the important role of molecular functional imaging in systematically exploring the disease biology and course of metastatic DTC is presented. Making this role the base, this report proposes a novel clinical classification for TENIS syndrome using molecular functional imaging. Such an endeavor, in our view, would aid in classification into subgroups and development of an individualized treatment strategy for patients with metastatic DTC. Case illustrations are presented that substantiate this viewpoint, including the value of combined assessment in selected cases and the requirement of a multipronged treatment approach for certain case scenarios. In addition to multiple other considerations, we believe that molecular functional imaging-based characterization of metastatic lesions could evolve as an important determinant for defining the optimal treatment strategy in patients with metastatic DTC, making the clinical management more rational and scientific.