Thyroid Cancer—Indications and Opportunities for Positron Emission Tomography/Computed Tomography Imaging

Positron Emission Tomography/Computed Tomography in Thyroid Cancer: An Updated Review

PET/computed tomography (CT) is a valuable hybrid imaging modality for the evaluation of thyroid cancer, potentially impacting management decisions. 18F-fluorodeoxyglucose (FDG) PET/CT has proven utility for recurrence evaluation in differentiated thyroid cancer (DTC) patients having thyroglobulin elevation with negative iodine scintigraphy. Aggressive histologic subtypes such as anaplastic thyroid cancer shower higher FDG uptake. 18F-FDOPA is the preferred PET tracer for medullary thyroid cancer. Fibroblast activation protein inhibitor and arginylglycylaspartic acid -based radiotracers have emerged as promising PET agents for radioiodine refractory DTC patients with the potential for theranostic application.

Role of PET/Computed Tomography in Elderly Thyroid Cancer: Tumor Biology and Clinical Management

PET/computed tomography (CT) studies can be potentially useful in elderly thyroid carcinoma patients for exploring the disease biology, especially in metastatic setting and thereby directing appropriate therapeutic management on case-to-case basis, adopting nuclear theranostics, and disease prognostication. With the availability of multiple PET radiopharmaceuticals, it would be worthwhile to evolve and optimally use FDG and the other non-fluorodeoxyglucose and investigational PET/CT tracers as per the clinical situation and need and thereby define their utilities in a given case scenario. In this regard, (I) differentiated thyroid carcinoma (DTC) including radioiodine refractory disease, poorly differentiated thyroid cancer (PDTC) and TENIS, (II) medullary thyroid carcinoma (MTC), (III) anaplastic carcinoma and (IV) Primary thyroid lymphoma (PTL) should be viewed and dealt separately.

Additive value of 18FDG-PET/CT to positive 131I whole body scan in recurrent differentiated thyroid cancer patients with potential influence on treatment strategy: single Egyptian center experience

Background

Years ago the utility of of18F-fluorodeoxyglucose-positron emission tomography/computerized tomography (18FDG-PET/CT) in differentiated thyroid cancer was confined mainly to cases with elevated serum thyroglobulin and negative 131I whole body scan. In this study, we try to assess the diagnostic performance of 18FDG-PET/CT in recurrent differentiated thyroid cancer patients with positive 131I whole body scan and in addition to evaluate the impact of 18FDG-PET/CT on the treatment strategy.

Results

The 18FDG PET/CT detected tumor recurrence in 35 (81.3%) patients most of them (91.4%) were in stage IV, while the rest 8.5% was in stage III. No recurrence was detected among patients in stage II and III by 18FDG PET/CT.

Regarding lesion-based analysis, sensitivity of 18FDG-PET/CT was superior to that of 131I post-therapeutic whole body scan (TxWBS) (78.2% vs. 69.4%, respectively), while both modalities had the same specificity (50%). 18FDG-PET/CT changed the treatment plan in 18 (41.6%) patients.

Conclusion

18FDG-PET/CT may be complementary to 131ITxWBS in high-risk DTC with impact on treatment strategy.

Advanced imaging and theranostics in thyroid cancer

PURPOSE OF REVIEW

Thyroid cancers are endocrine neoplasms with diverse gene expression and behavior, for which constantly evolving anatomic and functional imaging/theranostic agents have an essential role for diagnosis, staging, and treatment.

RECENT FINDINGS

To achieve definitive diagnosis, neck ultrasound and associated risk stratification systems, notably Thyroid Imaging Reporting and Data System (TI-RADS), allow improved thyroid nodule characterization and management guidance. Radioactive iodine-131 (RAI) has long played a role in management of differentiated thyroid cancer (DTC), with recent literature emphasizing its effectiveness for intermediate-high risk cancers, exploring use of dosimetry for personalized medicine, and potential for retreatment with RAI following tumor redifferentiation. Iodine-124 positron emission tomography/computed tomography (PET/CT) has promising application for DTC staging and dosimetry. F18-fluorodeoxyglucose (FDG) PET/CT is used for staging of high risk DTC and identification of noniodine-avid disease recurrences, with metabolic uptake consistently portending poor prognosis. Poorly differentiated and anaplastic thyroid cancers are best assessed with anatomic imaging and F18-FDG PET/ CT, though recent studies show a potential theranostic role for Ga68/Lu177-prostate-specific membrane antigen. Medullary thyroid cancers are evaluated with ultrasound, CT, magnetic resonance imaging, and various positron-emitting radiotracers for PET imaging (F18-DOPA, F18-FDG, and recently Ga68-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-octreotate (DOTATATE)); the latter may enable treatment with Lu177-DOTATATE.

SUMMARY

Multidisciplinary collaboration is essential to streamline appropriate management, given the wide array of available imaging and new therapies for metabolic and genetically complex cancers.

Role of Fluorodeoxyglucose-PET in Interventional Radiology

Fluorodeoxyglucose (FDG)-PET has expanding applications in the field of interventional radiology. FDG-PET provides both qualitative and quantitative assessments of malignancy, infection, and inflammation. These assessments can assist interventional radiologists in selecting the most appropriate treatment options for their oncology patients. FDG-PET is also useful for evaluating the response to interventional treatments and in predicting the prognosis of oncology patients. Finally, FDG-PET can assist the interventional radiologist in diagnosing and monitoring response to treatment of infection and inflammation. Nevertheless, there is a need for additional prospective studies to further establish the role of FDG-PET in these applications.

Molecular Imaging and Theragnostics of Thyroid Cancers

Molecular imaging plays an important role in the evaluation and management of different thyroid cancer histotypes. The existing risk stratification models can be refined, by incorporation of tumor-specific molecular markers that have theranostic power, to optimize patient-specific (individualized) treatment decisions. Molecular imaging with varying radioisotopes of iodine (i.e., ¹³¹I, ¹²³I, ¹²⁴I) is an indispensable component of dynamic and theragnostic risk stratification of differentiated carcinoma (DTC) while [¹⁸F]F-fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography/computed tomography (PET/CT) helps in addressing disease aggressiveness, detects distant metastases, and risk-stratifies patients with radioiodine-refractory DTC, poorly differentiated and anaplastic thyroid cancers. For medullary thyroid cancer (MTC), a neuroendocrine tumor derived from thyroid C-cells, [¹⁸F]F-dihydroxyphenylalanine (6-[¹⁸F]FDOPA) PET/CT and/or [¹⁸F]FDG PET/CT can be used dependent on serum markers levels and kinetics. In addition to radioiodine therapy for DTC, some theragnostic approaches are promising for metastatic MTC as well. Moreover, new redifferentiation strategies are now available to restore uptake in radioiodine-refractory DTC while new theragnostic approaches showed promising preliminary results for advanced and aggressive forms of follicular-cell derived thyroid cancers (i.e., peptide receptor radiotherapy). In order to help clinicians put the role of molecular imaging into perspective, the appropriate role and emerging opportunities for molecular imaging and theragnostics in thyroid cancer are discussed in our present review.

PET/CT Variants and Pitfalls in Head and Neck Cancers Including Thyroid Cancer

PET/CT imaging is a dual-modality diagnostic technology that merges metabolic and structural imaging. There are several currently available radiotracers, but ¹⁸F-FDG is the most commonly utilized due to its widespread availability. ¹⁸F-FDG PET/CT is a cornerstone of head and neck squamous cell carcinoma imaging. ⁶⁸Ga-DOTA-TOC is another widely used radiotracer. It allows for whole-body imaging of cellular somatostatin receptors, commonly expressed by neuroendocrine tumors and is the standard of reference for the characterization and staging of neuroendocrine tumors. The normal biodistribution of these PET radiotracers as well as the technical aspects of image acquisition and inadequate patient preparation affect the quality of PET/CT imaging. In addition, normal variants, artifacts and incidental findings may impede accurate image interpretation and can potentially lead to misdiagnosis. In order to correctly interpret PET/CT imaging, it is necessary to have a comprehensive knowledge of the normal anatomy of the head and neck and to be cognizant of potential imaging pitfalls. The interpreter must be familiar with benign conditions which may accumulate radiotracer potentially mimicking neoplastic processes and also be aware of malignancies which can demonstrate low radiotracer uptake. Appropriate use of structural imaging with either CT, MR or ultrasound can serve a complimentary role in several head and neck pathologies including local tumor staging, detection of bone marrow involvement or perineural spread, and classification of thyroid nodules. It is important to be aware of the role of these complementary modalities to maximize diagnostic accuracy and patient outcomes. The purpose of this article is to outline the basic principles of PET/CT imaging, with a focus on ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTA PET/CT. Basic physiology, variant imaging appearances and potential pitfalls of image interpretation are presented within the context of common use cases of PET technology in patients with head and neck cancers and other pathologies, benign and malignant.

AGGRESSIVE PAPILLARY CARCINOMA OF THE LATERAL ABERRANT THYROIDE: A CASE REPORT AND REVIEW OF THE LITERATTUREggressive papillary carcinoma of the lateral aberrant thyroide: A case report and review of the literatture

INTRODUCTION

Ectopic thyroid tissue can be found in many sites. Ectopic thyroid tissue may also be involved in the same processes as normal thyroid gland. These processes include tumors, inflammation and hyperplasia. The appearance of such tissue in rare locations may lead to diagnostic and therapeutic dilemmas.

PRESENTATION OF CCASE

We report a rare case of primary papillary carcinoma in an ectopic thyroid in the jugulocarotid regionbased on the bifurcation of the carotid artery, in a 62-year-old woman with history of diabetes and high blood pressure, with a normal thyroid gland.

DISCUSSION

The origin of lateral ectopic thyroid tissue is not fully understood and controversial.The lateral localisation is a rare entity and debated extensively in the literature.

CONCLUSION

Though rare, the possibility of an ectopic thyroid carcinoma must always be considered by the surgeon in cases of a pathological mass in the neck.

Thyroid cancer diagnosis in the era of precision imaging

Thyroid cancer affects 1.3% of the population with increasing rates of incidence over the last decade (approximately 2% per year). Although the overall prognosis is good in the differentiated subtypes, there has been a slow but steady increase in rate of deaths associated with thyroid cancer (approximately 0.7% per year over the last decade). Thyroid cancer is usually detected when: (I) patients feel a lump in the neck; (II) a routine clinical exam is performed; (III) an incidental thyroid nodule is identified on diagnostic imaging (e.g., CT neck or chest, carotid ultrasound, PET scan acquired for non-thyroid pathology). Identification of suspicious thyroid nodules results in further diagnostic work-up including laboratory assessment, further imaging, and biopsy. Accurate diagnosis is required for clinical staging and optimal patient treatment design. In this review, we aim to discuss utility of various imaging modalities and their role in thyroid cancer diagnosis and management. Additionally, we aim to highlight emerging diagnostic techniques that aim to improve diagnostic specificity and accuracy in thyroid cancer, thus paving way for precision medicine.

Adenine Nucleotide Translocase 2 as an Enzyme Related to [18F] FDG Accumulation in Various Cancers

PURPOSE

Although glucose transporter 1 (GLUT1) and hexokinase 2 (HK2) are known as major proteins involved in the molecular mechanisms for accumulating 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) in cancer cells, sometimes, [¹⁸F] FDG accumulation cannot be explained by the expression of these two proteins. We investigated the involvement of adenine nucleotide translocase 2 (ANT2), which catalyzes ADP/ATP exchange at the mitochondrial inner membrane, in [¹⁸F] FDG accumulation.

PROCEDURES

ANT2 expression was evaluated in various cancer cell lines and human cancer tissues (microarrays) using western blot and immunohistochemical (IHC) staining, respectively. The expression levels of ANT2 were compared to [¹⁸F] FDG accumulation and pathologic findings, including differentiation grade. Additionally, we modulated ANT2 expression levels using ANT2 siRNA and an ANT2 expression vector in cancer cells and murine xenografted tumors.

RESULTS

[¹⁸F] FDG accumulation correlated with ANT2 expression in various cancer cell lines; this was not explained by GLUT1 and/or HK2 expression. At both the cell and tissue levels, ANT2 expression was high in less-differentiated or more malignant type of cancers. [¹⁸F] FDG accumulation changed according to the modulation of the ANT2 expression level.

CONCLUSION

In various cancer cells and tissues, the expression levels of ANT2 explained [¹⁸F] FDG accumulation better than those of GLUT1 and HK2. ANT2 can be used as a marker of dedifferentiated pathology and aggressiveness of cancer.

Diagnostic role of F-18 FDG PET/CT for preoperative lymph node staging in thyroid cancer patients; A systematic review and metaanalysis

PURPOSE

Although ultrasonography (US) is a standard technique for the assessment of cervical lymph node (LN) metastasis, the role of F-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is increasingly reported. The purpose of this study is to assess the diagnostic accuracy of F-18 FDG PET-CT for detection of cervical LN metastasis in thyroid cancer (TCa) patients through a meta-analysis.

PATIENTS AND METHODS

The PubMed, Cochrane Database, and Embase from the earliest available date of indexing through September 31, 2019, were searched for studies evaluating the diagnostic performance of F-18 FDG PET-CT for detection of LN metastasis in TCa. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR-), and constructed summary receiver operating characteristic curves.

RESULTS

Across 9 studies (759 patients), the pooled sensitivity for F-18 FDG PET-CT for all cervical LN metastasis in TCa was 0.30 (95% CI; 0.26-0.35) a pooled specificity of 0.94. For central LN metastasis, the pooled sensitivity was 0.28 (95% CI; 0.21-0.34) and a pooled specificity was 0.87 (95% CI; 0.83-0.90). For lateral LN metastasis, the pooled sensitivity was 0.56 (95% CI; 0.50-0.62) and a pooled specificity was 0.94.

CONCLUSIONS

F-18 FDG PET-CT shows a low sensitivity and high specificity for the detection of metastatic LNs in patients with TCa. The current data suggests that F-18 FDG PET-CT is not indicated in the work up of patients with thyroid cancer or biochemical evidence of recurrent disease.

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.

Ectopic Papillary Thyroid Cancer with Distant Metastasis

Ectopic thyroid tissue is a rare clinical entity wherein malignant lesions may arise, the most common one being papillary carcinoma. We present a case of a 68-year-old female who presented with a growing mass in the right clavicle. An MR of the shoulder showed a soft tissue mass arising from the anterior margin of the right distal clavicle. A fine needle aspiration of the mass showed papillary thyroid carcinoma. PET/CT confirmed the clavicular and mediastinal mass. Excision of the clavicular mass and total thyroidectomy with modified right neck dissection were performed. Pathology revealed no evidence of malignancy in the thyroid; lymph nodes were positive for metastatic thyroid carcinoma. Postsurgery CT showed the superior mediastinal mass with surrounding adenopathy; radioiodine (RAI) treatment with dose of 142.1 mCi [5257.7 MBq] was recommended. Posttherapy whole-body scan (WBS) showed RAI avid tissue in the neck and superior mediastinum. Follow-up chest CT revealed pulmonary nodules that increased in number and size; a second RAI therapeutic dose was given. The posttherapy RAI WBS was negative. Repeat PET/CT showed multiple hypermetabolic lesions in the mediastinum, neck, lymph nodes, pulmonary nodes, and right shoulder. The FDG avid lesions with no RAI uptake suggested tumor dedifferentiation.

Diagnostic performance of PET in thyroid cancer with elevated anti-Tg Ab

We aimed to explore the role of the diagnostic accuracy of F-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) for the detection of recurrent and/or metastatic diseases in differentiated thyroid cancer (DTC) patients with progressively and/or persistently elevated TgAb levels and negative radioactive iodine whole-body scan (RI-WBS) through a systematic review and meta-analysis. The MEDLINE, EMBASE and Cochrane Library database, from the earliest available date of indexing through June 30, 2017, were searched for studies evaluating the diagnostic performance of F-18 FDG PET/CT for the detection of recurrent and/or metastatic diseases in DTC patients with progressively and/or persistently elevated TgAb levels and negative RI-WBS. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR-). Across 9 studies (515 patients), the pooled sensitivity for F-18 FDG PET/CT was 0.84 (95% CI; 0.77-0.89) a pooled specificity of 0.78 (95% CI; 0.67-0.86). Likelihood ratio (LR) syntheses gave an overall positive likelihood ratio (LR+) of 3.8 (95% CI; 2.5-5.7) and negative likelihood ratio (LR-) of 0.21 (95% CI; 0.14-0.30). The pooled diagnostic odds ratio (DOR) was 18 (95% CI; 10-34). The area (AUC) under the hierarchical summary receiver-operating characteristic (HCROC) curve was 0.88 (95% CI: 0.85-0.90). F-18 FDG PET or PET/CT demonstrated moderate sensitivity and specificity for the detection of recurrent and/or metastatic diseases in DTC patients with progressively and/or persistently elevated TgAb levels and negative RI-WBS.

Diagnostic value and therapeutic impact of 18F-FDG-PET/CT in differentiated thyroid cancer

The clinical significance of 18F-FDG-PET/CT in the follow-up of patients with differentiated thyroid carcinoma was evaluated and the results were compared with those of 18F-FDGPET, 131I-whole-body scintigraphy including SPECT/CT (WBS) and ultrasound. In addition, it was the aim to investigate the impact of 18F-FDG-PET/CT on the therapeutic management. Patients, methods: 327 patients (209 women, 118 men; mean age 53 ± 18 years) with differentiated thyroid cancer (242 papillary, 75 follicular, 6 mixed, 1 Hürthle cell and 3 poorly differentiated tumours) were analyzed retrospectively at four tertiary referral centres. 289 18F-FDG-PET/CT and 118 18F-FDG-PET studies were performed in these patients between 2007 and 2010. In addition, an overall clinical evaluation was performed, including cytology, histology, thyroglobulin level, ultrasound, WBS, and subsequent clinical course in order to compare the molecular imaging results. Finally, the change in therapeutic management due to findings of 18F-FDG-PET/CT was investigated. Results: The sensitivity of 18F-FDG-PET/CT was 92%, the specificity was 95%. Sensitivity and specificity of 18F-FDG-PET alone were 67% and 93%, respectively. WBS showed a sensitivity of 65% and a specificity of 94%. The corresponding values of ultrasound were 37% and 94%, respectively. The sensitivity of 18F-FDG-PET/CT in the group of patients with a negative WBS (n=194) amounted to 96%. When 18F-FDG-PET/CT and WBS were considered in combination, tumour tissue was missed in only 2 out of 133 patients; when 18F-FDG-PET and WBS were combined, tumour tissue was missed in 1 out of 24 patients. 18F-FDG-PET/CT resulted in management change in 43% (n=57/133) with a decision on surgical approach in 20% (n=27/133). Conclusions: 18F-FDG-PET/CT is superior to 18F-FDG-PET alone in patients with differentiated thyroid cancer and has a direct impact on the therapeutic management of patients with suspected local recurrence or metastases, particularly in those with negative WBS.

The role of FDG-PET in localization of recurrent lesions of differentiated thyroid cancer (DTC) in patients with asymptomatic hyperthyroglobulinemia in a real clinical practice

INTRODUCTION

Available methods, including serum thyroglobulin (Tg) measurement and whole-body scan (WBS) performed after radioiodine administration, allow for a precise diagnostics in differentiated thyroid cancer (DTC). However, some asymptomatic patients demonstrate negative WBS despite a high Tg serum concentration. In these subjects, fluorodeoxyglucose-positron emission tomography (FDG-PET) should be considered. The primary aim of our study was to evaluate a diagnostic value of FDG-PET in asymptomatic hyperthyroglobulinemia. The secondary one was to determine a prognostic value of a negative FDG-PET result in DTC patients with elevated Tg level.

MATERIAL

One hundred and ten FDG-PET/CT scans were retrospectively analyzed, 85 scans were done under TSH stimulation and 25 on LT4 suppressive therapy. Follow-up ranged between 4 and 9 years.

RESULTS

The first FDG-PET/CT detected cancer foci in 49 subjects with a global sensitivity of 45%. When the sensitivity was evaluated with reference to TSH stimulation and suppression, its values were 50 and 28% respectively. In 42 patients, FDG-PET failed to diagnose the reason for elevated Tg level. During further follow-up, in 17 of them, DTC recurrence was detected by other methods (CT, MRI, US). Fourteen subjects with asymptomatic hyperthyroglobulinemia were free of DTC progression for at least 4 years.

CONCLUSIONS

FDG-PET in DTC patients with asymptomatic hyperthyroglobulinemia constitutes a valuable diagnostic tool. Negative FDG-PET demonstrated a limited prognostic significance, as only every third patient did not show DTC progression. Moreover, negative FDG-PET does not justify less strict DTC monitoring, because it is related to 40% risk of relapse during the 5-year follow-up.

The role of early 18F-FDG PET/CT in therapeutic management and ongoing risk stratification of high/intermediate-risk thyroid carcinoma

Little is known about the role in ongoing risk stratification of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) performed early after radioactive iodine (RAI) ablation in differentiated thyroid carcinoma (DTC). The aim of the study is to investigate whether 18F-FDG PET/CT performed early after RAI ablation is useful to detect disease and to influence therapy and ongoing risk stratification. Patients with high/intermediate risk of recurrent DTC were included. 18F-FDG PET/CT scan was performed within 6 months after RAI ablation. We confirmed results with other imaging techniques, pathology reports, or follow-up. We classified the patient response as excellent, acceptable, or incomplete. Modified Hicks criteria were used to evaluate clinical impact. We included 81 patients with high/intermediate risk of recurrent DTC. Forty-one (50.6%) had positive uptake in 18F-FDG PET/CT, with negative (131)I whole-body scan ((131)I WBS). Sensitivity, specificity, and diagnostic accuracy of 18F-FDG PET/CT were 92.5, 90.2, and 91.4%, respectively. 18F-FDG PET/CT results had an impact on therapy in 38.3% of patients. One year after initial therapy, 45.7% showed excellent response, 8.6% acceptable response, and 45.7% incomplete response. A statistically significant relationship was found between negative 18F-FDG PET/CT and excellent response (80 vs. 12.2%, p < 0.001; OR 52.8). 18F-FDG PET/CT scan performed early in surveillance of patients with high/intermediate-risk thyroid carcinoma provides important additional information not available with conventional follow-up methods and had a high impact on therapy. A negative 18F-FDG PET/CT predicts an excellent response to therapy in the new ongoing risk stratification.

Clinical Utility of SPECT/CT Imaging Post-Radioiodine Therapy: Does It Enhance Patient Management in Thyroid Cancer?

BACKGROUND

The aim of this study was to evaluate post-therapy iodine-131 single-photon emission computed tomography/computed tomography ((131)I-SPECT/CT) imaging in comparison to conventional planar (131)I whole-body imaging, and to assess its clinical impact on the management of patients.

METHODS

We retrospectively reviewed planar (131)I whole-body and (131)I-SPECT/CT imaging findings in 67 patients who underwent (131)I therapy for thyroid cancer. Two nuclear medicine physicians reviewed the scans independently. The foci of increased tracer uptake were identified in the neck, thorax and elsewhere. Within the neck, the foci of (131)I-increased uptake were graded qualitatively as probable or definite uptake in thyroid remnants and probable or definite uptake in the lymph nodes. Serum thyroglobulin level, histopathology and other imaging findings served as the reference standard.

RESULTS

Of the 67 patients, 57 (85%) had radioiodine avid disease and 10 (15%) demonstrated non-radioiodine avid disease. Overall, post-therapy (131)I-SPECT/CT downstaged lymph node staging in 10 patients and upstaged it in 4 patients. This translated into a change of management for 9/57 (16%) patients with radioiodine avid disease. A change of management was observed in 5/10 patients with non-radioiodine avid disease confirmed in the post-(131)I-SPECT/CT study. Additionally, clinically significant findings such as incidental lung cancer, symptomatic pleural effusion and consolidation were also diagnosed in both groups of patients.

CONCLUSION

In patients with thyroid cancer, (131)I-SPECT/CT is a valuable addition to standard post-therapy planar imaging. SPECT/CT also improved diagnostic confidence and provided crucial clinical information leading to change of management for a significant number of these patients.

Nuclear Medicine in Thyroid Diseases in Pediatric and Adolescent Patients

Both benign and malignant diseases of the thyroid are rare in the pediatric and adolescent population, except congenital hypothyroidism. Nuclear medicine plays a major role, both in the diagnosis and therapy of thyroid pathologies. Use of radioactivity in pediatric population is strictly controlled due to possible side effects such as secondary cancers; therefore, management of pediatric patients requires detailed literature knowledge. This article aims to overview current algorithms in the management of thyroid diseases and use of radionuclide therapy in pediatric and adolescent population.

Clinical Usefulness of F-18 FDG PET/CT in Papillary Thyroid Cancer with Negative Radioiodine Scan and Elevated Thyroglobulin Level or Positive Anti-thyroglobulin Antibody

PURPOSE

Elevated thyroglobulin (Tg) levels, along with a negative radioiodine scan, present a clinical problem for the diagnosis of recurrence in papillary thyroid cancer (PTC) patients. The purpose of this study was to assess (1) the usefulness of (18)F-fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET)/computed tomography (CT) for PTC patients with negative diagnostic radioiodine scan and elevated serum Tg level or positive anti-thyroglobulin antibody (TgAb), and (2) the effect of endogenous thyroid stimulating hormone (TSH) stimulation (ETS) on detecting recurrence in these circumstances.

METHODS

Eighty-four patients with negative diagnostic radioiodine scan and elevated serum Tg or positive TgAb under ETS were included. Correlation with clinicopathological features and recurrence, detectability of FDG PET/CT and cut-off value of serum Tg for recurrence in PTC patients with these circumstance were assessed. In addition, detectability of F-18 FDG PET/CT under ETS and suppression were compared.

RESULTS

In Cox regression analysis, only serum Tg level was significantly associated with recurrence (P < 0.001, HR = 1.13; 95 % CI, 1.061-1.208). The cut-off level of Tg was 21.5 ng/mL (AUC, 0.919; P < 0.001) for discriminating the recurrence in the patients with positive PET/CT finding. The sensitivity, specificity, PPV, NPV, and accuracy of F-18 FDG PET/CT for detecting recurrence were 64 %, 94 %, 86 %, 81 %, and 83 %. In the analysis of F-18 FDG PET/CT under ETS, the sensitivity, specificity, PPV, NPV and accuracy was 64 %, 94 %, 88 %, 81 % and 83 %. Those under TSH suppression were 67 %, 92 %, 80 %, 85 % and 83 %.

CONCLUSIONS

F-18 FDG PET/CT, although less sensitive, showed high specificity, PPV, NPV, and accuracy and therefore can be useful for the patients with negative diagnostic radioiodine scan and elevated serum Tg or positive TgAb. In addition, FDG PET/CT under ETS does not seem to have an additive role in detecting recurrence in these patients.

Prognostic role of 18F-FDG PET/CT in the postoperative evaluation of differentiated thyroid cancer patients

PURPOSE

The aim of this study was to evaluate the role of F-FDG PET/CT performed after surgery but before radioiodine therapy in patients with differentiated thyroid cancer.

PROCEDURES

FDG PET/CT was performed off l-thyroxine in 60 newly diagnosed differentiated thyroid cancer patients. Clinical and hematological evaluation as well as high-resolution neck ultrasound were performed. All patients underwent a complete follow-up (range, 6-67 months; mean [SD], 31.7 [20.6] months). The date of recurrence or the most recent office visit was recorded. Progression-free survival (PFS) is the primary end point of this study. Analysis was performed by Cox proportional hazards model. Survival curves were generated using Kaplan-Meier estimates, and the log-rank test was used to assess significance.

RESULTS

FDG PET/CT was negative in 63% of patients, 20% had FDG thyroid bed uptake, 5% distant metastases, and 12% lymph node FDG uptake. In patients with positive FDG PET/CT scan (ie, those with distant metastases or lymph node uptake), a higher rate of recurrence was observed (50% vs 6%, P < 0.05). Thyroglobulin, neck ultrasound, stage, and FDG PET/CT correlated with PFS at univariate analysis. At multivariate analysis, only thyroglobulin and FDG PET/CT continued to be predictors of PFS. Patients with a negative FDG PET/CT scan have a better PFS either in the whole group or in those with elevated thyroglobulin level (both >2 ng/mL and >10 ng/mL).

CONCLUSIONS

FDG PET/CT was abnormal in 17% of patients. Moreover, FDG PET/CT has an independent prognostic role, with a better PFS in patients with a negative scan.

Clinical and molecular features of Hürthle cell carcinoma of the thyroid

CONTEXT

Hürthle cell cancer (HCC) of the thyroid remains the subject of controversy with respect to natural course, treatment, and follow-up.

OBJECTIVE

The objective of the study was to evaluate the clinical and molecular features associated with outcome in HCC.

DESIGN

The study was a review of 173 HCC cases treated at Mayo Clinic over 11 years with a median 5.8-year follow-up.

RESULTS

None of the patients with minimally invasive histology had persistent disease, clinical recurrence, or disease-related death. Male gender and TNM stage were independently associated with increased risk of clinical recurrence or death in widely invasive patients. The 5-year cumulative probability of clinical recurrence or death was higher in patients with TNM stage III-IV (females, 74%; males, 91%) compared with patients with TNM stage I-II (females, 0%; males, 17%). Pulmonary metastases were best identified by computed tomography, whereas radioactive iodine scans were positive in only two of 27 cases. Thyroglobulin was detectable in patients with clinical disease, with the notable exception of five patients with distant metastases. The common TERT C228T promoter mutation was detected in both widely invasive and minimally invasive tumors. TERT mRNA was below the limit of detection in all samples.

CONCLUSION

Widely invasive HCC with TNM stage III-IV is aggressive, with low probability of recurrence-free survival. Males have worse outcomes than females. Minimally invasive HCC appears to be considerably less aggressive. Radioactive iodine scan performs poorly in detecting distant disease. Although the TERT gene is mutated in HCC, the role of this mutation remains to be demonstrated.

PET/CT in the management of thyroid cancers

OBJECTIVE

Thyroid cancer is the most common endocrine cancer. This review evaluates the established use of (18)F-FDG PET/CT in papillary, follicular, Hürthle cell, anaplastic, and medullary thyroid cancers. The significance of incidental diffuse and focal thyroid FDG uptake is discussed. The evolving value of non-FDG radiotracers, including (124)I, (18)F-dihydroxyphenylalanine, and (68)Ga somatostatin analogs, is summarized.

CONCLUSION

PET/CT is a valuable imaging test, in the appropriate clinical context, for the management of thyroid cancers.

The Proportion of Malignancy in Incidental Thyroid Lesions on 18-FDG PET Study

Objective

To evaluate through a systematic review and meta-analysis the malignancy rates of thyroid incidentalomas identified in adults by 18-fluorodeoxyglucose positron emission tomography, computed tomography (18-FDG PET-CT) imaging studies.

Data Sources

The literature search was conducted using OVID Medline, EMBASE, the Cochrane Library, Google Scholar, Pubmed, and reference list review (inception to April 2013) by 2 independent review authors.

Review Methods

Studies with adults undergoing 18-FDG PET scan identifying a thyroid incidentaloma with definitive histological or cytological results reported were included.

Results

Thirty-one studies with a total of 197,296 PET studies and 3659 focal thyroid incidentalomas were identified with 1341 having definitive cytopathology or histopathology. The pooled proportion of malignancy was calculated as 19.8% (95% confidence interval [CI], 15.3%-24.7%) with 15.4% (95% CI, 11.4%-20.0%) of the total cases being papillary thyroid cancer. Distant metastases represented 1.1% (95% CI, 0.6%-1.8%) of the total cases.

Conclusions

Our systematic review and meta-analysis suggests that the incidence of malignancy is high in thyroid incidentalomas identified through 18-FDG PET imaging studies. Thyroid incidentalomas identified through 18-FDG PET require thorough investigation.

Recurrent thyroid cancer diagnosis: ROC study of the effect of a high-resolution head and neck 18F-FDG PET/CT scan

RATIONALE AND OBJECTIVES

(18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) has demonstrated significant value in the evaluation of patients with indication of recurrent thyroid cancer with negative conventional workup. The hypothesis of this study was that the addition of a dedicated, high-resolution head and neck scan (HNS) to the standard whole-body scan (WBS) improves the accuracy of the detection and diagnosis of recurrent thyroid cancer.

MATERIALS AND METHODS

Forty-three consecutive patients suspected for recurrent thyroid cancer, as indicated by increased tumor markers, prospectively underwent a WBS and a HNS with (18)F-FDG PET/CT. The patients were followed up to establish ground truth. A receiver operator characteristic (ROC) study with two observers was conducted to evaluate the impact of the additional HNS on the detection and diagnosis of recurrent thyroid cancer. Indices of performance included the area under the ROC curve (AUC), the number of detected abnormal foci, and the size of the detected foci without and with the HNS images.

RESULTS

ROC results showed that the addition of the HNS to the standard WBS increased the average AUC index of performance from 0.69 to 0.96, a statistically significant difference with a confidence interval (CI) of -0.33 to -0.19. Diagnosis was also improved with the average AUC increasing from 0.79 to 0.87 but differences were not statistically significant (CI, -0.19 to 0.04). Interreader agreement was "good" in the detection task and "excellent" in the diagnostic task. The addition of the HNS increased the number of detected foci in the positive patients by an average of 37%, whereas false-positive detections in the negative patients increased by an average of 10%. Reported average maximum lesion size also increased with the HNS addition by an average of 11%.

CONCLUSIONS

The addition of a high-resolution HNS to the standard whole-body PET/CT imaging improves readers' performance in the detection and diagnosis of recurrent thyroid cancer and could greatly benefit patient care.

Detectable thyroglobulin with negative imaging in differentiated thyroid cancer patients

In the absence of autoantibodies against thyroglobulin (Tg), Tg measurement nowadays is the cornerstone of clinical management of differentiated thyroid cancer patients. DTC patients presenting with a positive Tg measurement without an anatomical correlate on anatomic imaging provide a management challenge to the attending physician.

Based on the literature we will provide an overview of the most important steps to undertake in such patients and their potential clinical consequences.

Therapeutic impact of (18)F-FDG PET/CT in recurrent differentiated thyroid carcinoma

PURPOSE

(18)F-fluorodeoxyglucose-positron emission tomography/computed tomography (PET/CT) has proved effective in detecting recurrent or metastatic differentiated thyroid carcinoma (DTC) in the follow-up of operated DTC patients with high thyroglobulin (Tg) levels and negative findings on radioiodine whole-body scan. The aim of this retrospective study was to assess the impact of PET/CT on the planning of appropriate treatment for known recurrent disease in operated DTC patients.

MATERIALS AND METHODS

The study concerned 44 consecutive DTC patients (36 papillary, 8 follicular), who underwent total thyroidectomy and thyroid remnant ablation with (131)I and PET/CT. All patients had proven or strongly suspected recurrent disease judging from neck ultrasound (US) and fine-needle aspiration cytology, and detectable basal Tg levels.

RESULTS

PET/CT findings were positive in 25/44 patients (56.81 %) and negative in 19. A positive PET/CT result predicted resectable tumour recurrences in 19/25 patients, but also detected additional tumour sites that prompted changes to the treatment plan in 6/25 patients (24 %). A negative PET/CT result led to clinical monitoring for 11/19 patients (57.89 %).

CONCLUSIONS

PET/CT can help select patients, who might benefit from a tailored therapy by improving the detection of local recurrences not apparent on neck US or metastases.

PET and PET/CT imaging in thyroid and adrenal diseases: an update

Positron emission tomography (PET) and PET/computed tomography (PET/CT) with different tracers are imaging methods increasingly used in patients with thyroid and adrenal diseases. The aim of this article is to provide an overview based on literature data about the usefulness of PET imaging in this setting. PET and PET/CT with different tracers have been used in patients with thyroid diseases including differentiated thyroid carcinoma, medullary thyroid carcinoma, and poorly differentiated and anaplastic thyroid carcinoma. The usefulness of 18F-FDG-PET and PET/CT in assessing indeterminate thyroid nodules at fine needle aspiration biopsy and the clinical relevance of thyroid incidental 18F-FDG uptake has also been evaluated. Currently, great interest is being shown in a variety of PET tracers that target specific characteristics of adrenal gland function, allowing a more accurate characterization of adrenal masses and staging of adrenal tumors. Since PET/CT using different tracers is an expensive diagnostic tool which necessitates ionizing radiation exposure, cost-effectiveness studies are needed in order to define the appropriate use of this diagnostic method in various endocrine disorders.

The role of fluorine-18-fluorodeoxyglucose positron emission tomography in aggressive histological subtypes of thyroid cancer: an overview

Aggressive histological subtypes of thyroid cancer are rare and have a poor prognosis. The most important aggressive subtypes of thyroid cancer are Hürthle cell carcinoma (HCTC) and anaplastic and poorly differentiated carcinoma (ATC and PDTC). The American Thyroid Association recently published guidelines for the management of patients with ATC, but no specific guidelines have been done about HCTC. We performed an overview of the literature about the role of Fluorine-18-Fluorodeoxyglucose positron emission tomography or positron emission tomography/computed tomography (FDG-PET or PET/CT) in aggressive histological subtypes of thyroid cancer. Only few original studies about the role of FDG-PET or PET/CT in HCTC, PDTC, and ATC have been published in the literature. FDG-PET or PET/CT seems to be useful in staging or followup of invasive and metastatic HCTC. FDG-PET or PET/CT should be used in patients with ATC in initial staging and in the followup after surgery to evaluate metastatic disease. Some authors suggest the use of FDG-PET/CT in staging of PDTC, but more studies are needed to define the diagnostic use of FDG-PET/CT in this setting. Limited experience suggests the usefulness of FDG-PET or PET/CT in patients with more aggressive histological subtypes of DTC. However, DTC presenting as radioiodine refractory and FDG-PET positive should be considered aggressive tumours with poor prognosis.

The role of positron emission tomography and positron emission tomography/computed tomography in thyroid tumours: an overview

Positron emission tomography (PET) and PET/computed tomography (PET/CT) with different tracers have been increasingly used in patients with thyroid tumours. The aim of this article is to perform an overview based on literature data about the usefulness of PET imaging in this setting. The role of Fluorine-18-Fluorodeoxyglucose (FDG) PET and PET/CT in differentiated thyroid carcinoma (DTC) is well established, particularly in patients presenting with elevated serum thyroglobulin levels and negative radioiodine whole-body scan. Iodine-124 PET and PET/CT may serve a role in staging DTC and obtaining lesional dosimetry for a better and more rationale planning of treatment with Iodine-131. FDG-PET and PET/CT are useful in the post-thyroidectomy staging of high-risk patients with less differentiated histological subtypes. PET and PET/CT with different tracers seem to be useful methods in localizing the source of elevated calcitonin levels in patients with recurrent medullary thyroid carcinoma. Incorporation of FDG-PET or PET/CT into the initial workup of patients with indeterminate thyroid nodules at fine needle aspiration biopsy deserves further investigation. FDG-PET report should suggest further evaluation when focal thyroid incidentalomas are described because these findings are associated with a significant risk of cancer.

Detection of multiple disease indicators by an autonomous biomolecular computer

The promise of biomolecular computers is their ability to interact with naturally occurring biomolecules, enabling in the future the development of context-dependent programmable drugs. Here we show a context-sensing mechanism of a biomolecular automaton that can simultaneously sense different types of molecules, allowing future integration of biomedical knowledge on a broad range of molecular disease symptoms in the decision of a biomolecular computer to release a drug molecule.