The value of 18F-DOPA PET-CT in patients with medullary thyroid carcinoma: comparison with 18F-FDG PET-CT

Molecular imaging and related therapeutic options for medullary thyroid carcinoma: state of the art and future opportunities

Due to its rarity and non-specific clinical presentation, accurate diagnosis, and optimal therapeutic strategy of medullary thyroid carcinoma (MTC) remain challenging. Molecular imaging provides valuable tools for early disease detection, monitoring treatment response, and guiding personalized therapies. By enabling the visualization of molecular and cellular processes, these techniques contribute to a deeper understanding of disease mechanisms and the development of more effective clinical interventions. Different nuclear imaging techniques have been studied for assessing MTC, and among them, PET/CT utilizing multiple radiotracers has emerged as the most effective imaging method in clinical practice. This review aims to provide a comprehensive summary of the current use of advanced molecular imaging modalities, with a particular focus on PET/CT, for the management of patients with MTC. It aims to guide physicians towards a rationale for the use of molecular imaging also including theranostic approaches and novel therapeutical opportunities. Overall, we emphasize the evolving role of nuclear medicine in MTC. The integration of diagnostics and therapeutics by in vivo molecular imaging represents a major opportunity to personalize treatment for individual patients, with targeted radionuclide therapy being one representative example.

Sensitivities evaluation of five radiopharmaceuticals in four common medullary thyroid carcinoma metastatic sites on PET/CT: a network meta-analysis and systematic review

OBJECTIVES

Detecting medullary thyroid carcinoma (MTC) metastatic lesions accurately is still a challenge for clinicians. PET/computed tomography (PET/CT) seems to be the most effective method in recent years. However, the sensitivity of each radiopharmaceutical varies greatly in different metastatic sites. We aim to investigate and compare five novel and common PET or PET/CT radiopharmaceutical sensitivities at the four most frequent metastatic sites by network meta-analysis.

METHODS

We searched for studies evaluating PET/CT radiopharmaceutical sensitivities at different metastatic sites in PubMed, Web of Science, Embase, and Cochrane Library. The risk bias was analyzed, and publication bias was accessed by funnel plot asymmetry tests. We performed both global inconsistency and local inconsistency tests by evaluating the agreement between direct and indirect comparisons. Then, we made pairwise meta-analyses and network meta-analyses for each metastatic site. Finally, we performed the surface under the cumulative ranking curves (SUCRA) and calculated the SUCRA values to rank the probability of each radiopharmaceutical being the most sensitive method.

RESULTS

In our results, 243 patients from 9 clinical studies which accessed sensitivities of different radiopharmaceuticals in MTC metastatic sites were included. For lymph nodes and liver, TF2/ 68 Ga-SSM288 showed the highest SUCRA values (0.974 in lymph nodes, 0.979 in liver). The SUCRA values for 18 F-DOPA and 68 Ga-SSA for bone metastatic lesions were nearly identical (0.301 and 0.319, respectively) and were higher than the other three radiopharmaceuticals. For lung lesions, 11 C-methionine had the highest SUCRA value (0.412).

CONCLUSION

TF2/ 68 Ga-SSM288 had the best sensitivity in lymph nodes and liver lesions. 11 C-methionine was most sensitive in lung lesions. While 18 F-DOPA and 68 Ga-SSA had familiar sensitivities to be the best two radiopharmaceuticals.

Functional imaging in thyroid cancer patients with metastases and therapeutic implications

Functional imaging plays a central role in the management of thyroid cancer patients. In patients with a differentiated thyroid cancer (DTC), radioactive iodine (RAI) is used mostly with a therapeutic intent, either post-operatively or as the first line systemic treatment in patients with known structural disease. A whole body scan is performed a few days after the RAI administration, and this procedure is very sensitive to detect all tumor foci with RAI uptake. PET/CT with ¹⁸F-FDG complements the use of RAI at the initial evaluation of patients with high-risk DTC, during follow-up in those with rising serum thyroglobulin levels over time, for the work-up of patients with documented structural disease and for assessing the efficacy of focal or systemic treatment modalities. ¹⁸F-FDG uptake is a prognostic indicator in all these clinical conditions. A dosimetric approach with ¹²⁴I PET/CT showed encouraging results. Several functional imaging modalities are currently available for medullary thyroid carcinoma (MTC) patients. ¹⁸F-FDG-PET/CT may be sensitive in MTC patients with high FDG uptake that signals aggressive disease. ¹⁸F-DOPA is the most sensitive imaging technique to visualize small tumor foci, and is also highly specific in patients with a known MTC, but should be complemented by a CT scan of the chest and by a MRI of the liver to detect small metastases.

Imaging medullary thyroid cancer patients with detectable serum markers: state of the art and future perspectives

PURPOSE

Medullary thyroid carcinoma (MTC) originates from thyroid parafollicular C-cells and represents <5% of all thyroid cancers. Serum Calcitonin (CTn) is considered the most sensitive marker of persistent or recurrent disease and is measured in association to CEA. According to the American Thyroid Association (ATA) guidelines, following initial surgery when CTn level remains below 150 pg/mL, follow-up may rely on repeated serum marker determinations and on neck ultrasonography (US). When CTn level exceeds 150 pg/ml, additional imaging is required. In this review, we provide an overview of available imaging tools to monitor MTC course and propose an effective imaging strategy for MTC patients according to their clinical situation.

METHODS

A literature search focusing on available imaging tools to monitor MTC provided the currently available information for this review. Recent evidence-based reports and reviews were considered as priority over older evidence.

RESULTS

For MTC patients with detectable CTn levels and disease recurrence, PET/CT imaging with ¹⁸F-DOPA or ⁶⁸Ga-DOTA-peptides present the best sensitivity for lesion detection. ¹⁸F FDG PET/CT represents a prognostic tool and is useful in case of aggressive disease. Neck ultrasound, chest CT scan and MRI of the liver and of the axial skeleton represent complementary techniques. Beyond the diagnostic accuracy, the clinical impact of imaging is variable according to different disease settings and tumor marker levels. Finally, other applications of imaging such as response to focal and systemic treatments and new promising PET tracers should be further investigated.

CONCLUSION

The role of imaging in MTC patients improved, especially with the use of ¹⁸F-DOPA PET/CT that provides high quality diagnostic images. However, the impact on therapeutic management should be further evaluated in the different disease settings and in proper prospective trials.

Medullary thyroid carcinoma

PURPOSE OF REVIEW

To summarize recent developments in the diagnosis and management of patients with medullary thyroid cancer (MTC), with a focus on pathogenesis, systemic therapy, and future directions.

RECENT FINDINGS

The addition of mutational analysis to cytological assessment of thyroid nodules has improved the diagnostic accuracy of MTC. The discovery of new genomic alterations and overexpression of certain factors allows for improved prognostication in MTC and provides potentially new therapeutic agents. New data suggest that tumor environment may be more immunogenic than previously thought in a subset of MTCs with identification of a new MTC-specific antigen leading to a revival of investigating immune-based therapy for this disease. The newly approved selective rearranged during transfection (RET0-inhibitors, selpercatinib and pralsetinib, offer promising results, and tolerability for patients with RET-mutated MTC; however, the development of resistance mechanisms may be problematic.

SUMMARY

MTC has witnessed remarkable advancements in recent years. Our new understanding of some of the driver mutations in MTC allows for therapeutics with more tolerable adverse event profiles. However, there is still a need for more effective treatment strategies for subsets of patients without actionable mutations and for those who develop resistance to currently available therapies.

Evaluation of F-18 DOPA PET/CT in the detection of recurrent or metastatic medullary thyroid carcinoma: comparison with GA-68 DOTA-TATE PET/CT

OBJECTIVE

PET imaging with F-18 DOPA (FDOPA) and Ga-68 DOTATATE (TATE) shows the most promising results to detect medullary thyroid cancer (MTC) recurrence. We performed this comparative study to detect the site of recurrent or metastatic disease in MTC patients with elevated serum calcitonin (Ctn) and/or carcinoembryonic antigen (CEA) levels.

METHODS

We studied 46 MTC patients (25 women, 21 men) with elevated Ctn and/or CEA levels during follow-up who had both FDOPA and TATE PET/CT scans for re-staging purposes.

RESULTS

FDOPA PET imaging yielded an overall sensitivity of 86.8%, specificity of 100%, PPV of 100%, NPV of 61.5%, and accuracy of 89.1%, while TATE PET scan had the same values as 84.2%, 87.5%, 96.9%, 53.8%, and 84.6%, respectively, and there was no statistically significant difference between the two modalities with the exception of the specificity value that was higher for FDOPA imaging. In a subgroup of patients with overt Ctn or CEA elevation, sensitivity of FDOPA increased significantly, whereas TATE sensitivity did not change. FDOPA PET imaging was significantly superior in detecting liver and regional lymph node (LN) metastases, while TATE PET scan was significantly better in the skeletal metastases. Early FDOPA demonstrated 11 invisible lesions on late FDOPA.

CONCLUSION

Both FDOPA and TATE PET/CT imaging are useful to localize recurrences in MTC patients. While TATE imaging is superior to reveal skeletal disease, FDOPA seems better in liver and regional LN metastases; therefore, the two modalities appear complementary in monitoring MTC patients with elevated serum Ctn and/or CEA levels.

Next-Generation Molecular Imaging of Thyroid Cancer

An essential aspect of thyroid cancer (TC) management is personalized and precision medicine. Functional imaging of TC with radioiodine and [18F]FDG has been frequently used in disease evaluation for several decades now. Recently, advances in molecular imaging have led to the development of novel tracers based on aptamer, peptide, antibody, nanobody, antibody fragment, and nanoparticle platforms. The emerging targets-including HER2, CD54, SHP2, CD33, and more-are promising targets for clinical translation soon. The significance of these tracers may be realized by outlining the way they support the management of TC. The provided examples focus on where preclinical investigations can be translated. Furthermore, advances in the molecular imaging of TC may inspire the development of novel therapeutic or theranostic tracers. In this review, we summarize TC-targeting probes which include transporter-based and immuno-based imaging moieties. We summarize the most recent evidence in this field and outline how these emerging strategies may potentially optimize clinical practice.

The correlation between tumor markers and Ga-68 DOTA-TATE PET/CT findings in patients with advanced medullary thyroid cancer

BACKGROUND

Medullary thyroid cancer is a rare type of neuroendocrine tumor. Calcitonin (Ctn) and carcinoembryonic antigen (CEA) are used as markers for medullary thyroid cancer. The aim of the study was to evaluate the importance of serum Ctn and CEA levels in predicting total tumor volume.

MATERIAL AND METHODS

Ga-68 DOTA-TATE PET/CT findings such as whole-body somatostatin receptor-expressing metabolic tumor volume (SSR-E MTV) and total lesion volume (SSR-E TLV) were calculated and correlation analysis was done for tumor markers and whole-body SSR-E MTV and TLV.

RESULTS

A total of 28 patients with advanced medullary thyroid cancer were included in this retrospective study. In the correlation analysis, there was a statistically significant positive correlation between Ctn and whole-body SSR-E MTV (rho=0.503 and P=.008). Similarly, significant positive correlation was observed between Ctn and whole-body SSR-E TLV (rho=0.436 and P=.023). There was a significant positive correlation between CEA and whole-body SSR-E MTV (rho=0.584 and P=.007). Also, a positive correlation was observed between CEA and whole-body SSR-E TLV (rho=0.436 and P=.023). These correlations were most marked in patients with Ctn≥152pg/mL and/or both nodal and bone involvement.

CONCLUSION

These results could stimulate clinicians to perform Ga-68 PET for treatment decisions, especially in patients with high CEA and Ctn levels at the time of diagnosis.

Comparison of 5 Different PET Radiopharmaceuticals for the Detection of Recurrent Medullary Thyroid Carcinoma: A Network Meta-analysis

PURPOSE

The aim of this study is to investigate and compare the performance of different PET radiopharmaceuticals for the detection of recurrent medullary thyroid carcinoma (MTC) by performing a network meta-analysis (NMA) using direct comparison studies with 2 or more PET radiopharmaceuticals.

METHODS

PubMed and EMBASE were searched for the studies evaluating the performance of PET or PET/CT for the detection of recurrent MTC. The NMA was performed for different PET radiopharmaceuticals in both patient- and lesion-based analyses and with a threshold of serum calcitonin or carcinoembryonic antigen (CEA) levels and calcitonin doubling time. The consistency was evaluated by examining the agreement between direct and indirect treatment effects, and publication bias was assessed by funnel plot asymmetry tests. The surface under the cumulative ranking curve values were obtained to calculate the probability of each PET modality being the most effective diagnostic method.

RESULTS

A total of 306 patients from 14 direct comparison studies using 5 different PET radiopharmaceuticals (F-FDG, F-DOPA, Ga-somatostatin analogs, 3-O-methyl-6-[F]fluoro-DOPA, and C-methionine) for the detection of recurrent MTC was included. The detection rate of F-DOPA PET was significantly higher than that of FDG PET in both patient- and lesion-based analyses (patient-based analysis: odds ratio, 2.44; 95% confidence interval, 1.4-4.31; lesion-based analysis: odds ratio, 5.74; 95% confidence interval, 1.65-23.4). Among all PET radiopharmaceuticals, F-DOPA showed the highest surface under the cumulative ranking curve value in both patient- and lesion-based analyses regardless of serum calcitonin or CEA levels and calcitonin doubling time.

CONCLUSIONS

The results from this NMA indicate that F-DOPA PET clearly showed a best performance for the detection of recurrent MTC in both patient- and lesion-based analyses regardless of serum calcitonin or CEA levels and calcitonin doubling time.

Amino Acid Transporters as Potential Therapeutic Targets in Thyroid Cancer

Thyroid cancer cells have a high amino acid demand for proliferation, invasion, and metastasis. Amino acids are taken up by thyroid cancer cells, both thyroid follicular cell and thyroid parafollicular cells (commonly called "C-cells"), via amino acid transporters. Amino acid transporters up-regulate in many cancers, and their expression level associate with clinical aggressiveness and prognosis. This is the review to discuss the therapeutic potential of amino acid transporters and as molecular targets in thyroid cancer.

Which Is the Optimal Scan Time of 18F-DOPA PET/CT in Patients With Recurrent Medullary Thyroid Carcinoma?: Results From a Dynamic Acquisition Study

PURPOSE

The aim of this retrospective study was to determine, by dynamic acquisition, the optimal scan time of F-DOPA PET/CT in patients with recurrent medullary thyroid carcinoma (MTC).

METHODS

Twenty-one patients with suspected recurrent MTC underwent dynamic F-DOPA PET/CT (lasting 45 minutes) followed by whole-body scan. Three different time intervals of dynamic acquisition were evaluated: ultra-early phase (2-5 minutes), early phase (5-10 minutes), and late phase (40-45 minutes). The number and SUVmax of all detected lesions among the 3 dynamic acquisition phases were compared on qualitative and semiquantitative analyses. Time-activity curves, SUVmax washout rate between ultra-early or early phase and late phase, and signal-to-noise ratio (SNR) between lesion and background activity were also calculated.

RESULTS

At dynamic acquisition, 15 of 21 patients were classified as PET-positive and 6 of 21 as PET-negative, with overall 21 detected lesions. Ultra-early and early imaging provided a better lesion visualization than late phase in more than 70% of cases, as also reflected by SNR (mean SNR reduction between 2 and 45 minutes, -45% ± 19%). Time-activity curves showed a rapid tracer accumulation in MTC lesions, with an average maximum uptake at 2 minutes after injection. Mean lesion SUVmax was 2-fold higher in ultra-early frames compared with last frames (mean washout rate, -44% ± 33%). Finally, compared with whole-body imaging in the same field of view, dynamic acquisition identified 1 additional positive patient and 3 additional lesions in 2 patients.

CONCLUSIONS

Our study, showing a very fast F-DOPA uptake in MTC lesions, suggests the utility to obtain early PET/CT images, already at 2 to 5 minutes after tracer injection, when maximum lesion tracer uptake is reached.

The added diagnostic value of complementary gadoxetic acid-enhanced MRI to 18F-DOPA-PET/CT for liver staging in medullary thyroid carcinoma

Background

A high proportion of patients with advanced stages of medullary thyroid carcinoma (MTC) present with liver metastasis metastases. The aim of our study was to investigate the added diagnostic value of complementary gadoxetic acid-enhanced MRI to ¹⁸F-DOPA-PET/CT for liver staging in MTC.

Methods

Thirty-six patients (14 female, median age 55 years) with histologically confirmed MTC undergoing gadoxetic acid-enhanced liver MRI within 1 month of matching contrast-enhanced ¹⁸F-DOPA-PET/CT between 2010 and 2016 were selected for this IRB-approved retrospective study. ¹⁸F-DOPA-PET/CT and multiparametric MRI data sets were read consecutively and liver lesions were categorised on a 5-point Likert scale (1–definitely benign; 2–probably benign; 3–intermediate risk for metastasis; 4–probably metastasis; 5–definitely metastasis). It was noted if gadoxetic acid-enhanced MRI detected additional, ¹⁸F-DOPA-PET/CT-occult metastases (category 5) or if gadoxetic acid-enhanced MRI allowed for a definite classification (categories 1 and 5) of lesions for which ¹⁸F-DOPA-PET/CT remained inconclusive (categories 2–4). Follow-up PET/CT and MRI examinations were used as a reference standard.

Results

A total of 207 liver lesions (¹⁸F-DOPA-PET/CT 149, MRI 207; 152 metastases, 37 benign cysts, 18 hemangiomas) were analysed. Fifty-eight additional lesions were detected by MRI, of which 54 were metastases (median diameter 0.5 cm [interquartile range 0.4–0.7 cm]) occult on ¹⁸F-DOPA-PET/CT. MRI allowed for a definite lesion classification (categories 1 and 5) in 92% (190/207) whereas ¹⁸F-DOPA-PET/CT allowed for a definite lesion classification in 76% (113/149). MRI lead to a change in lesion categorisation in 14% (21/149).

Conclusion

Gadoxetic acid-enhanced MRI allows for a more precise liver staging in MTC patients compared to ¹⁸F-DOPA-PET/CT alone, particularly for ¹⁸F-DOPA-negative metastases and lesions < 1 cm.

European Association of Nuclear Medicine Practice Guideline/Society of Nuclear Medicine and Molecular Imaging Procedure Standard 2019 for radionuclide imaging of phaeochromocytoma and paraganglioma

PURPOSE

Diverse radionuclide imaging techniques are available for the diagnosis, staging, and follow-up of phaeochromocytoma and paraganglioma (PPGL). Beyond their ability to detect and localise the disease, these imaging approaches variably characterise these tumours at the cellular and molecular levels and can guide therapy. Here we present updated guidelines jointly approved by the EANM and SNMMI for assisting nuclear medicine practitioners in not only the selection and performance of currently available single-photon emission computed tomography and positron emission tomography procedures, but also the interpretation and reporting of the results.

METHODS

Guidelines from related fields and relevant literature have been considered in consultation with leading experts involved in the management of PPGL. The provided information should be applied according to local laws and regulations as well as the availability of various radiopharmaceuticals.

CONCLUSION

Since the European Association of Nuclear Medicine 2012 guidelines, the excellent results obtained with gallium-68 (68Ga)-labelled somatostatin analogues (SSAs) in recent years have simplified the imaging approach for PPGL patients that can also be used for selecting patients for peptide receptor radionuclide therapy as a potential alternative or complement to the traditional theranostic approach with iodine-123 (123I)/iodine-131 (131I)-labelled meta-iodobenzylguanidine. Genomic characterisation of subgroups with differing risk of lesion development and subsequent metastatic spread is refining the use of molecular imaging in the personalised approach to hereditary PPGL patients for detection, staging, and follow-up surveillance.

Novel PET tracers: added value for endocrine disorders

Nuclear medicine has been implicated in the diagnosis and treatment of endocrine disorders for several decades. With recent development of PET tracers, functional imaging now plays a major role in endocrine tumors enabling with high performance to their localization, characterization, and staging. Besides ¹⁸F-FDG, which may be used in the management and follow-up of endocrine tumors, new tracers have emerged, such as ¹⁸F-DOPA for neuroendocrine tumors (NETs) (medullary thyroid carcinoma, pheochromocytomas and paragangliomas and well-differentiated NETs originating from the midgut) and ¹⁸F-Choline in the field of primary hyperparathyroidism. Moreover, some peptides such as somatostatin analogs can also be used for peptide receptor radionuclide therapy. In this context, Gallium-68 labeled somatostatin analogs (⁶⁸Ga-SSA) can help to tailor therapeutic choices and follow the response to treatment in the so-called "theranostic" approach. This review emphasizes the usefulness of these three novel PET tracers (¹⁸F-Choline, ¹⁸F-FDOPA, and ⁶⁸Ga-SSA) for primary hyperparathyroidism and neuroendocrine tumors.

Medullary Thyroid Carcinoma: Do Ultrasonography and F-DOPA-PET-CT Influence the Initial Surgical Strategy?

Background

At the time of diagnosis, one-third of medullary thyroid carcinoma (MTC) patients show lymph node (LN) or distant metastasis. A metastasized MTC requires different surgical strategies.

Objective

This study aimed to determine the value of ultrasound and [18F]fluoro-dihydroxyphenylalanine positron emission tomography with computed tomography (F-DOPA-PET-CT) in localizing MTC, as well as LN and distant metastasis.

Methods

The study included 50 patients (24 males/26 females) with preoperative ultrasound, F-DOPA-PET-CT, and histologically proven MTC. Imaging results were correlated with both preoperative basal calcitonin (bCt) levels and final histology.

Results

Tumors were classified as pT1a:17 (diameter, mean ± standard deviation: 5.8 ± 3.0 mm), pT1b:15 (15.0 ± 3.2 mm), pT2:9 (27.3 ± 7.0 mm), and pT3:9 (38.3 ± 24.2 mm). The median bCt level was 202 pg/mL (lower/upper quartile: 82/1074 pg/mL). Ultrasound was positive for tumor in 45/50 (92%) patients (20.0 ± 16.0 mm) and negative in 5 patients (3.2 ± 2.2 mm). Overall, 43/50 (86%) patients had positive F-DOPA local scans (20.0 ± 16.4 mm), while 7 (14%) patients were negative (7.7 ± 8.1 mm). Lastly, 21/50 (42%) patients had LN metastasis; 8/21 (38%) patients had positive LNs suspected with ultrasound, and 12/21 (57%) patients had positive LNs suspected with F-DOPA. Tumor and LN sensitivity of ultrasound was 92% and 43%, respectively, and 86% and 57% of F-DOPA-PET-CT, respectively. In 3/50 (6%) patients and 3/50 (6%) patients, mediastinal LN metastasis and distant metastasis, respectively, were diagnosed only by F-DOPA-PET-CT.

Conclusion

Ultrasound and F-DOPA-PET-CT are sensitive for the localization of MTC but not for the presence and location of LN metastasis (limitations: size/number). Only F-DOPA ensures the diagnosis of distant metastasis and influences the extent of LN surgery. Surgical strategy cannot be predicted based on neither ultrasound nor F-DOPA-PET-CT.

Comparison of 68Ga PET/CT to Other Imaging Studies in Medullary Thyroid Cancer: Superiority in Detecting Bone Metastases

CONTEXT

Persistent disease after surgery is common in medullary thyroid cancer (MTC), requiring lifelong radiological surveillance. Staging workup includes imaging of neck, chest, abdomen, and bones. A study integrating all sites would be ideal. Despite the established use of gallium-68 (68Ga) positron emission tomography (PET)/CT with somatostatin analogues in most neuroendocrine tumors, its efficacy is controversial in MTC.

OBJECTIVE

Evaluate the efficacy of 68Ga PET/CT in detecting MTC lesions and evaluate tumor expression of somatostatin receptors (SSTRs) associated with 68Ga PET/CT findings.

METHODS

Prospective study evaluating 30 patients with MTC [group 1 (n = 16), biochemical disease; group 2 (n = 14), metastatic disease]. Patients underwent 68Ga PET/CT, bone scan, CT and ultrasound of the neck, CT of the chest, CT/MRI of the abdomen, and MRI of the spine. 68Ga PET/CT findings were analyzed by disease site as positive or negative and as concordant or discordant with conventional studies. Sensitivity and specificity were calculated using pathological or cytological analysis or unequivocal identification by standard imaging studies. Immunohistochemical analysis of SSTRs was compared with 68Ga PET/CT findings.

RESULTS

In both groups, 68Ga PET/CT was inferior to currently used imaging studies except for bone scan. In group 2, 68Ga PET/CT sensitivities were 56%, 57%, and 9% for detecting neck lymph nodes, lung metastases, and liver metastases, respectively, and 100% for bone metastases, superior to the bone scan (44%). Expression of SSTRs, observed in 44% of tumors, was not associated with 68Ga-DOTATATE uptake.

CONCLUSIONS

68Ga PET/CT does not provide optimal whole-body imaging as a single procedure in patients with MTC. However, it is highly sensitive in detecting bone lesions and could be a substitute for a bone scan and MRI.

Histology-proven recurrence in the lateral or central neck after systematic neck dissection for medullary thyroid cancer

PURPOSE

To delineate risk factors for, and examine temporal patterns of, histology-proven recurrent medullary thyroid cancer (MTC) after compartment-oriented surgery.

METHODS

Multivariate Cox regression on overall, node, and soft tissue infiltrate recurrence per previously dissected neck compartment.

RESULTS

Mean follow-up for the 203 (and 158) patients with central (and ipsilateral lateral) neck dissection was 56.1 months. On multivariate Cox regression, tumor size > 20 mm predicted overall and node recurrence in the central neck, whereas extranodal growth predicted overall and node recurrence in the ipsilateral lateral neck. Extrathyroidal extension alone predicted soft tissue infiltrate recurrence in the central neck, and extranodal growth alone soft tissue infiltrate recurrence in the ipsilateral lateral neck. When analyses were restricted to patients not biochemically cured after initial surgery, only extranodal growth predicted overall and node recurrence in the dissected neck compartments.

CONCLUSIONS

Patients not biochemically cured, specifically those with extranodal growth at the initial operation, carry greater risks of node recurrence.

[18F]DOPA PET/ceCT in diagnosis and staging of primary medullary thyroid carcinoma prior to surgery

Purpose

Medullary thyroid carcinoma (MTC) is characterized by a high rate of metastasis. In this study we evaluated the ability of [¹⁸F]DOPA PET/ceCT to stage MTC in patients with suspicious thyroid nodules and pathologically elevated serum calcitonin (Ctn) levels prior to total thyroidectomy and lymph node (LN) dissection.

Methods

A group of 32 patients with sonographically suspicious thyroid nodules and pathologically elevated basal Ctn (bCtn) and stimulated Ctn (sCtn) levels underwent DOPA PET/ceCT prior to surgery. Postoperative histology served as the standard of reference for ultrasonography and DOPA PET/ceCT region-based LN staging. Univariate and multivariate regression analyses as well as receiver operating characteristic analysis were used to evaluate the correlations between preoperative and histological parameters and postoperative tumour persistence or relapse.

Results

Primary MTC was histologically verified in all patients. Of the 32 patients, 28 showed increased DOPA decarboxylase activity in the primary tumour (sensitivity 88%, mean SUVmax 10.5). Undetected tumours were exclusively staged pT1a. The sensitivities of DOPA PET in the detection of central and lateral metastatic neck LN were 53% and 73%, in contrast to 20% and 39%, respectively, for neck ultrasonography. Preoperative bCtn and carcinoembryonic antigen levels as well as cN1b status and the number of involved neck regions on DOPA PET/ceCT were predictive of postoperative tumour persistence/relapse in the univariate regression analysis (P < 0.05). Only DOPA PET/ceCT cN1b status remained significant in the multivariate analysis (P = 0.016, relative risk 4.02).

Conclusion

This study revealed that DOPA PET/ceCT has high sensitivity in the detection of primary MTC and superior sensitivity in the detection of LN metastases compared to ultrasonography. DOPA PET/ceCT identification of N1b status predicts postoperative tumour persistence. Thus, implementation of a DOPA-guided LN dissection might improve surgical success.

18F-Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography for Other Thyroid Cancers: Medullary, Anaplastic, Lymphoma and So Forth

Positron emission tomography/computed tomography (PET/CT) with ¹⁸F-fluorodeoxyglucose (FDG) is used in staging, restaging, and evaluation of therapy response in many cancers as well as differentiated thyroid carcinomas especially in non-iodine avid variants. Its potential in less frequent thyroid tumors like medullary, anaplastic thyroid cancers, thyroid lymphoma and metastatic tumors of the thyroid however, is not well established yet. The aim of this review is to provide an overview on the recent applications and indications of ¹⁸F-FDG PET/CT in these tumors and to focus on the controversies in the clinical setting.

Dynamic risk stratification for medullary thyroid cancer according to the response to initial therapy

Detecting persistent/recurrent disease of medullary thyroid carcinoma (MTC) is important. The tumor-node-metastasis (TNM) staging system is useful for predicting disease-specific mortality, but is a static system and does not include postoperative serum calcitonin levels. We have focused on the clinical usefulness of dynamic risk stratification (DRS) using the best response to the initial therapy in MTC patients. A total of 120 MTC patients were classified into three DRS groups based on their responses to initial therapy. Clinical outcomes were assessed according to TNM staging and DRS. In the DRS, 70, 23 and 7 % of the MTC patients were classified into excellent, biochemical incomplete, or structural incomplete response groups, respectively. On TNM staging, 37, 16, 13 and 35 % of patients were stages I-IV, respectively. There were significant differences in survivals according to TNM staging (p = 0.03) and DRS (p = 0.005). During the median follow-up of 6.2 years, 75 patients (63 %) demonstrated no evidence of disease (NED). About 60 and 17 % of patients in stages III and IV were NED, respectively. DRS predicted NED better than TNM staging according to the proportion of variance explained (PVE) (49.1 vs. 28.7 %, respectively). At the final follow-up, 88, 4 and 0 % of patients in excellent, biochemical incomplete, and structural incomplete response groups attained NED, respectively. DRS based on the best response to the initial therapy can provide useful prognostic information in addition to initial TNM staging for predicting of mortality, as well as the likelihood of NED in MTC patients.

Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma

INTRODUCTION

The American Thyroid Association appointed a Task Force of experts to revise the original Medullary Thyroid Carcinoma: Management Guidelines of the American Thyroid Association.

METHODS

The Task Force identified relevant articles using a systematic PubMed search, supplemented with additional published materials, and then created evidence-based recommendations, which were set in categories using criteria adapted from the United States Preventive Services Task Force Agency for Healthcare Research and Quality. The original guidelines provided abundant source material and an excellent organizational structure that served as the basis for the current revised document.

RESULTS

The revised guidelines are focused primarily on the diagnosis and treatment of patients with sporadic medullary thyroid carcinoma (MTC) and hereditary MTC.

CONCLUSIONS

The Task Force developed 67 evidence-based recommendations to assist clinicians in the care of patients with MTC. The Task Force considers the recommendations to represent current, rational, and optimal medical practice.

Radiopharmaceuticals as probes to characterize tumour tissue

Tumour cells exhibit several properties that allow them to grow and divide. A number of these properties are detectable by nuclear imaging methods. We discuss crucial tumour properties that can be described by current radioprobe technologies, further discuss areas of emerging radioprobe development, and finally articulate need areas that our field should aspire to develop. The review focuses largely on positron emission tomography and draws upon the seminal 'Hallmarks of Cancer' review article by Hanahan and Weinberg in 2011 placing into context the present and future roles of radiotracer imaging in characterizing tumours.

Neuroendocrine tumors: beyond the abdomen

Several classification systems for neuroendocrine tumors (NETs) exist, which use variable terminology and criteria for grading and staging. This variability in terminology can cause confusion and difficulty in recognizing which tumors are, in fact, members of this heterogeneous group of malignancies. The largest group of NETs, the gastroenteropancreatic NETs, has been well described and characterized; however, there are less-recognized extra-abdominal NETs that can arise from nearly any organ in the body. In this article, the clinical features and imaging appearances of the extra-abdominal NETs will be reviewed, compared, and contrasted. This diverse group consists of paragangliomas, Merkel cell carcinomas, esthesioneuroblastomas, NETs of the lung, and medullary thyroid carcinomas. Recognition of these tumors as part of the larger group of NETs is important for understanding how best to approach imaging for their diagnosis, staging, and potential treatment. Familiarity with the computed tomographic and magnetic resonance imaging appearances and the role of radionuclide imaging of these heterogeneous groups aids in the correct diagnosis and in treatment planning.

Role of (18) F-FDOPA PET/CT imaging in endocrinology

(18) F-FDOPA (6-[18F]-L-fluoro-L-3, 4-dihydroxyphenylalanine)-based PET/CT imaging can be a useful tool for the detection of different neuroendocrine tumours (NETs). (18) F-FDOPA is taken up into the cells via the neutral amino acid transporter (LAT1/4F2hc). This transporter is also coupled to the mammalian target of rapamycin (mTOR) signalling pathway. (18) F-FDOPA PET/CT may be performed for confirmation of diagnosis of pheochromocytoma/paraganglioma, staging at initial presentation, restaging and follow-up of patients. In SDHx-related syndromes, (18) F-FDG PET/CT should be performed in addition to (18) F-FDOPA PET/CT. (18) F-FDOPA PET/CT is also invaluable in the detection staging/restaging of carcinoid tumours and has greater sensitivity as compared to somatostatin receptor scintigraphy. (18) F-FDOPA PET/CT can also distinguish between focal vs diffuse CHI. It is not as useful in adult hyperinsulinism due to increased background uptake, but the problem may be overcome with the help of premedication with carbidopa. It has limited use in pancreatic NETs. (18) F-FDOPA PET/CT is a good modality for detection of persistent and residual medullary thyroid cancer (MTC), but (18) F-FDG PET/CT may be needed in aggressive tumours. In summary, F-DOPA PET/CT has widespread utility in the diagnosis of different neuroendocrine tumours.

Diagnosis and preoperative imaging of multiple endocrine neoplasia type 2: current status and future directions

Multiple endocrine neoplasia type 2 (MEN2) is a rare autosomal dominant syndrome caused by mutations in the RET protooncogene and is characterized by a strong penetrance of medullary thyroid carcinoma (all subtypes) and is often accompanied by pheochromocytoma (MEN2A/2B) and primary hyperparathyroidism (MEN2A). The evaluation and management of MEN2-related tumours is often different from that of sporadic counterparts. This review article provides an overview of clinical manifestations, diagnosis and surgical management of MEN2 patients. This review also presents applications of the most up-to-date imaging modalities to MEN2 patients that are tightly linked to the clinical management and aims to guide physicians towards a rationale for the use of imaging prior to prophylactic thyroidectomy, initial surgery and reoperations for persistent/recurrent disease. This review also concludes that, in the near future, it is expected that these patients will indeed benefit from newly developed positron emission tomography approaches which will target peptide receptors and protein kinases. Identification of MEN2-specific radiopharmaceuticals will also soon arise from molecular profiling studies. Furthermore, subtotal (cortical-sparing) adrenalectomy, which is a valid option in MEN2 for avoiding long-term steroid replacement, will benefit from an accurate estimation through imaging of differential adrenocortical function.

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.

Congenital hyperinsulinism: Role of fluorine-18L-3, 4 hydroxyphenylalanine positron emission tomography scanning

Congenital hyperinsulinism (CHI) is a rare but complex heterogeneous disorder caused by unregulated secretion of insulin from the β-cells of the pancreas leading to severe hypoglycaemia and neuroglycopaenia. Swift diagnosis and institution of appropriate management is crucial to prevent or minimise adverse neurodevelopmental outcome in children with CHI. Histologically there are two major subtypes of CHI, diffuse and focal disease and the management approach will significantly differ depending on the type of the lesion. Patients with medically unresponsive diffuse disease require a near total pancreatectomy, which then leads on to the development of iatrogenic diabetes mellitus and pancreatic exocrine insufficiency. However patients with focal disease only require a limited pancreatectomy to remove only the focal lesion thus providing complete cure to the patient. Hence the preoperative differentiation of the histological subtypes of CHI becomes paramount in the management of CHI. Fluorine-18L-3, 4-hydroxyphenylalanine positron emission tomography (¹⁸F-DOPA-PET) is now the gold standard for pre-operative differentiation of focal from diffuse disease and localisation of the focal lesion. The aim of this review article is to give a clinical overview of CHI, then review the role of dopamine in β-cell physiology and finally discuss the role of ¹⁸F-DOPA-PET imaging in the management of CHI.

Update on medullary thyroid cancer

Medullary thyroid carcinoma (MTC) is a rare type of thyroid cancer, demonstrating variable behavior from indolent disease to highly aggressive, progressive disease. There are distinguishing phenotypic features of sporadic and hereditary MTC. Activation or overexpression of cell surface receptors and up-regulation of intracellular signaling pathways in hereditary and sporadic MTC are involved in the disease pathogenesis. There has been an exponential rise in clinical trials with investigational agents, leading to approval of 2 medications for progressive, advanced MTC. Developments in understanding the pathogenesis of MTC will hopefully lead to more effective and less toxic treatments of this rare but difficult to treat cancer.

Normal biodistribution pattern and physiologic variants of 18F-DOPA PET imaging

Dihydroxyphenylalanine (DOPA) is a neutral amino acid that resembles natural l-dopa (dopamine precursor). It enters the catecholamine metabolic pathway of endogenous l-DOPA in the brain and peripheral tissues. It is amenable to labeling with fluorine-18 (¹⁸F) for PET imaging and was originally used in patients with Parkinson’s disease to assess the integrity of the striatal dopaminergic system. The recent introduction and use of hybrid PET/CT scanners has contributed significantly to the management of a series of other pathologies including neuroendocrine tumors, brain tumors, and pancreatic cell hyperplasia. These pathologic entities present an increased activity of l-DOPA decarboxylase and therefore demonstrate high uptake of ¹⁸F-DOPA. Despite these potentially promising applications in several clinical fields, the role of ¹⁸F-DOPA has not been elucidated completely yet because of associated difficulties in synthesis and availability. Unfortunately, the available literature does not provide recommendations for procedures or administered activity, acquisition timing, and premedication with carbidopa. The aim of this paper is to outline the physiological biodistribution and normal variants, including possible pitfalls that may lead to misinterpretations of the scans in various clinical settings.

¹⁸F-DOPA PET/computed tomography imaging

18F-DOPA is a radiopharmaceutical with interesting clinical applications and promising performances in the evaluation of the integrity of dopaminergic pathways, brain tumors, NETs (especially MTCs, paragangliomas, and pheochromocytomas), and congenital hyperinsulinism. 18F-DOPA traces a very specific metabolic pathway and has a very precise biodistribution pattern. As for any radiopharmaceutical, the knowledge of the normal distribution of 18F-DOPA, its physiologic variants, and its possible pitfalls is essential for the correct interpretation of PET scans. Moreover, it is important to be aware of the potential false-positive and false-negative episodes that can occur in the various clinical settings.

Current update on medullary thyroid carcinoma

OBJECTIVE

This article will review the multimodality imaging spectrum of medullary thyroid carcinoma (MTC) with an emphasis on anatomic and functional imaging. Recent advances in the molecular cytogenetics of this tumor and the impact on diagnosis, prognosis, and development of novel targeted therapy will be discussed.

CONCLUSION

MTC is a neuroendocrine tumor with unique clinicopathologic and radiologic features compared with other thyroid malignancies. Imaging plays an important role in the optimal management of this malignancy.

Comparison of different positron emission tomography tracers in patients with recurrent medullary thyroid carcinoma: our experience and a review of the literature

Several morphological and functional imaging techniques are usually used to detect residual/recurrent medullary thyroid carcinoma (MTC) with variable results; currently, there is growing interest in positron emission tomography (PET) methodology. Herein, we report our experience of and a literature review about the comparison of different positron emission tomography (PET) tracers in patients with residual/recurrent MTC. (18)F-DOPA PET/CT seems to be the most useful imaging method to detect recurrent MTC lesions, performing better than (18)F-FDG and (68)Ga-somatostatin analogs PET/CT. (18)F-FDG may complement (18)F-DOPA in patients with aggressive tumors. (68)Ga-somatostatin analogs PET/CT may be useful to select patients who could benefit from radioreceptor therapy. The information provided by the various PET tracers reflects different metabolic pathways, and may help to select the most appropriate treatment.

[Oncologic imaging: indications for and limitations of modern cross-sectional imaging techniques]

Cross-sectional imaging techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) CT are an integral part of the modern oncological workup. They are used for tumor detection and staging as well as for treatment evaluation and monitoring. Due to pathophysiological and histological differences there is no universal imaging protocol for the assessment of different forms of cancer. For instance, CT is still the standard technique for the detection and staging of lung cancer supplemented by PET which aids the exclusion of nodal involvement and the detection of distant metastases. For hepatocellular carcinoma on the other hand, MRI is the preferred imaging technique, particularly when used in conjunction with liver-specific contrast media - PET/CT is only of limited value. Finally, for neuroendocrine tumors there is a focus on special radiotracers, which, in the context of PET/CT, enable a highly specific whole-body assessment. Thus, knowledge of the pathophysiological and imaging characteristics of different tumors is essential for a personalized, state-of-the art management of oncology patients.

18F-fluorodihydroxyphenylalanine vs other radiopharmaceuticals for imaging neuroendocrine tumours according to their type

6-Fluoro-(¹⁸F)-L-3,4-dihydroxyphenylalanine (FDOPA) is an amino acid analogue for positron emission tomography (PET) imaging which has been registered since 2006 in several European Union (EU) countries and by several pharmaceutical firms. Neuroendocrine tumour (NET) imaging is part of its registered indications. NET functional imaging is a very competitive niche, competitors of FDOPA being two well-established radiopharmaceuticals for scintigraphy, ¹²³I-metaiodobenzylguanidine (MIBG) and ¹¹¹In-pentetreotide, and even more radiopharmaceuticals for PET, including fluorodeoxyglucose (FDG) and somatostatin analogues. Nevertheless, there is no universal single photon emission computed tomography (SPECT) or PET tracer for NET imaging, at least for the moment. FDOPA, as the other PET tracers, is superior in diagnostic performance in a limited number of precise NET types which are currently medullary thyroid cancer, catecholamine-producing tumours with a low aggressiveness and well-differentiated carcinoid tumours of the midgut, and in cases of congenital hyperinsulinism. This article reports on diagnostic performance and impact on management of FDOPA according to the NET type, emphasising the results of comparative studies with other radiopharmaceuticals. By pooling the results of the published studies with a defined standard of truth, patient-based sensitivity to detect recurrent medullary thyroid cancer was 70 % [95 % confidence interval (CI) 62.1–77.6] for FDOPA vs 44 % (95 % CI 35–53.4) for FDG; patient-based sensitivity to detect phaeochromocytoma/paraganglioma was 94 % (95 % CI 91.4–97.1) for FDOPA vs 69 % (95 % CI 60.2–77.1) for ¹²³I-MIBG; and patient-based sensitivity to detect midgut NET was 89 % (95 % CI 80.3–95.3) for FDOPA vs 80 % (95 % CI 69.2–88.4) for somatostatin receptor scintigraphy with a larger gap in lesion-based sensitivity (97 vs 49 %). Previously unpublished FDOPA results from our team are reported in some rare NET, such as small cell prostate cancer, or in emerging indications, such as metastatic NET of unknown primary (CUP-NET) or adrenocorticotropic hormone (ACTH) ectopic production. An evidence-based strategy in NET functional imaging is as yet affected by a low number of comparative studies. Then the suggested diagnostic trees, being a consequence of the analysis of present data, could be modified, for some indications, by a wider experience mainly involving face-to-face studies comparing FDOPA and ⁶⁸Ga-labelled peptides.