18F-dihydroxyphenylalanine PET in patients with biochemical evidence of medullary thyroid cancer: relation to tumor differentiation

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.

Development of the First 18F-Labeled Radiohybrid-Based Minigastrin Derivative with High Target Affinity and Tumor Accumulation by Substitution of the Chelating Moiety

In order to optimize elevated kidney retention of previously reported minigastrin derivatives, we substituted (R)-DOTAGA by DOTA in (R)-DOTAGA-rhCCK-16/-18. CCK-2R-mediated internalization and affinity of the new compounds were determined using AR42J cells. Biodistribution and µSPECT/CT imaging studies at 1 and 24 h p.i. were carried out in AR42J tumor-bearing CB17-SCID mice. Both DOTA-containing minigastrin analogs exhibited 3- to 5-fold better IC50 values than their (R)-DOTAGA-counterparts. natLu-labeled peptides revealed higher CCK-2R affinity than their natGa-labeled analogs. In vivo, tumor uptake at 24 h p.i. of the most affine compound, [19F]F-[177Lu]Lu-DOTA-rhCCK-18, was 1.5- and 13-fold higher compared to its (R)-DOTAGA derivative and the reference compound, [177Lu]Lu-DOTA-PP-F11N, respectively. However, activity levels in the kidneys were elevated as well. At 1 h p.i., tumor and kidney accumulation of [19F]F-[177Lu]Lu-DOTA-rhCCK-18 and [18F]F-[natLu]Lu-DOTA-rhCCK-18 was high. We could demonstrate that the choice of chelators and radiometals has a significant impact on CCK-2R affinity and thus tumor uptake of minigastrin analogs. While elevated kidney retention of [19F]F-[177Lu]Lu-DOTA-rhCCK-18 has to be further addressed with regard to radioligand therapy, its radiohybrid analog, [18F]F-[natLu]Lu-DOTA-rhCCK-18, might be ideal for positron emission tomography (PET) imaging due to its high tumor accumulation at 1 h p.i. and the attractive physical properties of fluorine-18.

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.

State of the art and future directions in the systemic treatment of medullary thyroid cancer

PURPOSE OF REVIEW

Systemic treatment is the only therapeutic option for patients with progressive, metastatic medullary thyroid cancer (MTC). Since the discovery of the rearranged during transfection (RET) proto-oncogene (100% hereditary, 60-90% sporadic MTC), research has focused on finding effective systemic therapies to target this mutation. This review surveys recent findings.

RECENT FINDINGS

Multikinase inhibitors are systemic agents targeting angiogenesis, inhibiting growth of tumor cells and cells in the tumor environment and healthy endothelium. In the phase III EXAM and ZETA trials, cabozantinib and vandetanib showed progression-free survival benefit, without evidence of prolonged overall survival. Selpercatinib and pralsetinib are kinase inhibitors with high specificity for RET; phase I and II studies showed overall response rates of 73% and 71% in first line, and 69% and 60% in second line treatment, respectively. Although resistance mechanisms to mutation-driven therapy will be a challenge in the future, phase III studies are ongoing and neo-adjuvant therapy with selpercatinib is being studied.

SUMMARY

The development of selective RET-inhibitors has expanded the therapeutic arsenal to control tumor growth in progressive MTC, with fewer adverse effects than multikinase inhibitors. Future studies should confirm their effectiveness, study neo-adjuvant strategies, and tackle resistance to these inhibitors, ultimately to improve patient outcomes.

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.

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.

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.

Innovative imaging of insulinoma: the end of sampling? A review

Receptors for the incretin glucagon-like peptide-1 (GLP-1R) have been found overexpressed in selected types of human tumors and may, therefore, play an increasingly important role in endocrine gastrointestinal tumor management. In particular, virtually all benign insulinomas express GLP-1R in high density. Targeting GLP-1R with indium-111, technetium-99m or gallium-68-labeled exendin-4 offers a new approach that permits the successful localization of small benign insulinomas. It is likely that this new non-invasive technique has the potential to replace the invasive localization of insulinomas by selective arterial stimulation and venous sampling. In contrast to benign insulinomas, malignant insulin-secreting neuroendocrine tumors express GLP-1R in only one-third of the cases, while they more often express the somatostatin subtype 2 receptors. Importantly, one of the two receptors appears to be always overexpressed. In special cases of endogenous hyperinsulinemic hypoglycemia (EHH), that is, in the context of MEN-1 or adult nesidioblastosis GLP-1R imaging is useful whereas in postprandial hypoglycemia in the context of bariatric surgery, GLP-1R imaging is probably not helpful. This review focuses on the potential use of GLP-1R imaging in the differential diagnosis of EHH.

F-18-Dopa Positron Emission Tomography/Computed Tomography Is More Sensitive Than Whole-Body Magnetic Resonance Imaging for the Localization of Persistent/Recurrent Disease of Medullary Thyroid Cancer Patients

Background: Elevated postoperative serum calcitonin (Ctn) level indicates persistent/recurrent disease in patients with medullary thyroid carcinoma (MTC). Its location is a challenge. The aim of our study was to compare the disease detection rates of F-18-Dopa (fluoro dihydroxyphenylalanine) positron emission tomography (PET)/computed tomography (CT), whole-body (WB) magnetic resonance imaging (MRI), F-18-FDG (fluorodeoxyglucose) PET/CT, WB CT scanning, neck ultrasonography, and bone scintigraphy in MTC patients with increased Ctn levels and unknown localization of the source. Methods: We compared the independent reading of each imaging procedure with a reference assessment for structural disease defined by pathology or concordance between two imagings or with subsequent follow-up. The detection rate of each imaging modality was determined in per patient, per organ, and per lesion analysis. Results: Thirty-six consecutive patients (21 females, mean age: 57 years, sporadic MTC in 26 cases, median serum Ctn level: 760 pg/mL; range: 21-10,121) were analyzed. The reference assessment localized disease in 24 (64%) patients with 74 lesions detected in the thyroid bed (8), in neck lymph nodes (15), mediastinal lymph nodes (6), lungs (1), liver (2), bones (3), and other site (1). At the patient level, the detection rates were 64% (CI 0.48-0.80) for F-18-Dopa PET/CT with early acquisitions, 40% (CI 0.24-0.56) for F-18-FDG PET/CT, 40% (CI 0.24-0.56) for WB MRI, and 48% (CI 0.31-0.66) for WB CT scan. Conclusions: In MTC patients with increased Ctn and no known distant metastases, F-18-Dopa PET/CT is more sensitive to detect structural disease than any other imaging modality, including WB MRI.

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.

Recent Development of Nuclear Molecular Imaging in Thyroid Cancer

Therapies targeting specific tumor pathways are easy to enter the clinic. To monitor molecular changes, cellular processes, and tumor microenvironment, molecular imaging is becoming the key technology for personalized medicine because of its high efficacy and low side effects. Thyroid cancer is the most common endocrine malignancy, and its theranostic radioiodine has been widely used to diagnose or treat differentiated thyroid cancer. This article summarizes recent development of molecular imaging in thyroid cancer, which may accelerate the development of personalized thyroid cancer therapy.

Thyroid Cancer: Risk-Stratified Management and Individualized Therapy

Thyroid cancer is the most common endocrine malignancy. Differentiated thyroid cancer (DTC) with the two subtypes, papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC), is the most frequent subtype of thyroid cancer; more rare subtypes are medullary thyroid cancer (MTC) and anaplastic thyroid cancer (ATC). The incidence of DTC has increased rapidly in recent years due to the more frequent use of imaging methods such as ultrasound of the neck and fine-needle aspiration (FNA) of thyroid nodules. After total thyroidectomy and radioiodine treatment, DTC remains an indolent and curable disease in most patients, whereas the cure rate in MTC is lower and depends on early diagnosis. Most ATCs are incurable. In recent years, there has been great progress in identifying genetic changes in thyroid cancer, and genetic testing of FNA samples or blood samples provides useful information for clinical decision making. Tumor staging, either postoperatively or by imaging, and measuring the tumor markers thyroglobulin for DTC and calcitonin for MTC, allow for dynamic risk-adapted stratification for follow-up procedures. In advanced metastatic thyroid cancer, molecular targeted therapy using tyrosine kinase receptor inhibitors, including sorafenib, lenvantinib, vandetanib, and cabozantinib, helps control tumor progression and prolongs progression-free survival. Using a dynamic risk-stratified approach to manage thyroid cancer, the outcomes for most thyroid cancer patients are excellent compared with those for other cancers. The major challenge in the future is to identify high-risk patients and to treat and monitor them appropriately. Clin Cancer Res; 22(20); 5012-21. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "ENDOCRINE CANCERS REVISING PARADIGMS".

Predictive and prognostic value of 18F-DOPA PET/CT in patients affected by recurrent medullary carcinoma of the thyroid

INTRODUCTION

Medullary thyroid carcinoma (MTC) is a malignancy accounting for about 5-8% of thyroid cancers. Serum calcitonin and carcinoembryonic antigen (CEA) levels are widely used to monitor disease progression. However, prognostic factors able to predict outcomes are highly desirable. We, therefore, aimed to assess the prognostic role of ¹⁸F-DOPA PET/CT in patients with recurrent MTC.

MATERIALS AND METHODS

60 patients (mean age 64 ± 13 years, range 44-82) with recurrent MTC were eligible from a multicenter database. All patients underwent a restaging ¹⁸F-DOPA PET/CT, performed at least 6 months after surgery. CEA/calcitonin levels, local recurrences, nodal involvement and metastases at PET/CT were recorded. SUVmax, SUVmean (also normalized to mediastinal uptake) and metabolic tumor volume were automatically calculated for each lesion, by placing a volume of interest around the lesion with 40% of peak activity as threshold for the automatic contouring. The patients were clinically and radiologically followed up for 21 ± 11 months. Rate of progression-free survival (PFS), disease-specific survival (DSS) and incremental prognostic value of ¹⁸F-DOPA PET/CT over conventional imaging modalities were assessed by Kaplan-Meier curves and Log-Rank test. Cox regression univariate and multivariate analyses were performed for assessing predictors of prognosis.

RESULTS

¹⁸F-DOPA PET/CT showed abnormal findings in 27 patients (45%) and resulted unremarkable in 33 (55%). PFS was significantly longer in patients with an unremarkable PET/CT scan (p = 0.018). Similarly, an unremarkable PET/CT study was associated with a significantly longer DSS (p = 0.04). ¹⁸F-DOPA PET/CT added prognostic value over other imaging modalities both for PFS and for DSS (p < 0.001 and p = 0.012, respectively). Neither semiquantitative PET parameters nor clinical or laboratory data were predictive of a worse PFS and DSS in patients with recurrent MTC.

CONCLUSION

¹⁸F-DOPA PET/CT scan has an important prognostic value in predicting disease progression and mortality rate.

Macrocalcitonin Is a Novel Pitfall in the Routine of Serum Calcitonin Immunoassay

CONTEXT

Calcitonin (CT) is a sensitive marker of medullary thyroid carcinoma (MTC) and is used for primary diagnosis and follow-up after thyroidectomy. However, persistently elevated CT is observed even after complete surgical removal without evidence of a recurrent or persistent tumor.

OBJECTIVE

To investigate the presence of assay interference in the serum CT of MTC patients who are apparently without a structural disease.

PATIENTS AND METHODS

We studied three index MTC cases for CT assay interference and 14 patients with metastatic MTC. The CT level was measured using an immunofluorometric assay. Screening for assay interference was performed by determination of CT levels before and after serum treatment with polyethylene glycol. Additionally, samples were analyzed by chromatography on ultra-performance liquid chromatography and protein A-Sepharose.

RESULTS

Patients with biochemical and structural disease showed CT mean recovery of 84.1% after polyethylene glycol treatment, whereas patients suspected of interference showed recovery from 2-7%. The elution profile on UPLC showed that the immunometric CT from these three patients behaved like a high molecular mass aggregate (>300 kDa). Additionally, when these samples were applied to the protein A-Sepharose, CT immunoreactivity was retained on the column and was only released after lowering the pH.

CONCLUSIONS

For the first time, our results show the presence of a novel pitfall in the CT immunoassay: "macrocalcitonin." Its etiology, frequency, and meaning remain to be defined, but its recognition is of interest and can help clinicians avoid unnecessary diagnostic investigations and treatment during the follow-up of MTC.

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.

Endocrine tumours: progressive metastatic medullary thyroid carcinoma: first- and second-line strategies

The treatment for metastasised medullary thyroid cancer is still a topic of discussion. One of the main challenges remains to find effective adjuvant and palliative options for patients with metastatic disease. The diagnostic and treatment strategies for this tumour are discussed and possible new developments commented. Approaches that target rearranged during transfection (RET) are preferable to those that target RET downstream proteins as, theoretically, blocking RET downstream targets will block only one of the many pathways activated by RET. Combining several agents would seem to be more promising, in particular agents that target RET with those that independently target RET signalling pathways or the more general mechanism of tumour progression.

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.

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.

18F-FDOPA PET/CT imaging of insulinoma revisited

PURPOSE

(18)F-FDOPA PET imaging is increasingly used in the work-up of patients with neuroendocrine tumours. It has been shown to be of limited value in localizing pancreatic insulin-secreting tumours in adults with hyperinsulinaemic hypoglycaemia (HH) mainly due to (18)F-FDOPA uptake by the whole pancreatic gland. The objective of this study was to review our experience with (18)F-FDOPA PET/CT imaging with carbidopa (CD) premedication in patients with HH in comparison with PET/CT studies performed without CD premedication in an independent population.

METHODS

A retrospective study including 16 HH patients who were investigated between January 2011 and December 2013 using (18)F-FDOPA PET/CT (17 examinations) in two academic endocrine tumour centres was conducted. All PET/CT examinations were performed under CD premedication (200 mg orally, 1 - 2 h prior to tracer injection). The PET/CT acquisition protocol included an early acquisition (5 min after (18)F-FDOPA injection) centred over the upper abdomen and a delayed whole-body acquisition starting 20 - 30 min later. An independent series of eight consecutive patients with HH and investigated before 2011 were considered for comparison. All patients had a reference whole-body PET/CT scan performed about 1 h after (18)F-FDOPA injection. In all cases, PET/CT was performed without CD premedication.

RESULTS

In the study group, (18)F-FDOPA PET/CT with CD premedication was positive in 8 out of 11 patients with histologically proven insulinoma (73 %). All (18)F-FDOPA PET/CT-avid insulinomas were detected on early images and 5 of 11 (45 %) on delayed ones. The tumour/normal pancreas uptake ratio was not significantly different between early and delayed acquisitions. Considering all patients with HH, including those without imaging evidence of disease, the detection rate of the primary lesions using CD-assisted (18)F-FDOPA PET/CT was 53 %, showing 9 insulinomas in 17 studies performed. In the control group (without CD premedication, eight patients), the final diagnosis was benign insulinoma in four, nesidioblastosis in one, and no definitive diagnosis in the remainder. (18)F-FDOPA PET/CT failed to detect any tumour in these patients.

CONCLUSION

According to our experience, CD administration before (18)F-FDOPA injection leads to low residual pancreatic (18)F-FDOPA activity preserving tumoral uptake with consequent insulinoma detection in more than half of adult patients with HH and more than 70 % of patients with a final diagnosis of insulinoma. If (18)F-FDOPA PET/CT is indicated, we strongly recommend combining CD premedication with early acquisition centred over the pancreas.

Diagnóstico, tratamento e seguimento do carcinoma medular de tireoide: recomendações do Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia

Introdução O carcinoma medular de tireoide (CMT) origina-se das células parafoliculares da tireoide e corresponde a 3-4% das neoplasias malignas da glândula. Aproximadamente 25% dos casos de CMT são hereditários e decorrentes de mutações ativadoras no proto-oncogene RET (REarranged during Transfection). O CMT é uma neoplasia de curso indolente, com taxas de sobrevida dependentes do estádio tumoral ao diagnóstico. Este artigo descreve diretrizes baseadas em evidências clínicas para o diagnóstico, tratamento e seguimento do CMT. Objetivo O presente consenso, elaborado por especialistas brasileiros e patrocinado pelo Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia, visa abordar o diagnóstico, tratamento e seguimento dos pacientes com CMT, de acordo com as evidências mais recentes da literatura. Materiais e métodos: Após estruturação das questões clínicas, foi realizada busca das evidências disponíveis na literatura, inicialmente na base de dados do MedLine-PubMed e posteriormente nas bases Embase e SciELO – Lilacs. A força das evidências, avaliada pelo sistema de classificação de Oxford, foi estabelecida a partir do desenho de estudo utilizado, considerando-se a melhor evidência disponível para cada questão. Resultados Foram definidas 11 questões sobre o diagnóstico, 8 sobre o tratamento cirúrgico e 13 questões abordando o seguimento do CMT, totalizando 32 recomendações. Como um todo, o artigo aborda o diagnóstico clínico e molecular, o tratamento cirúrgico inicial, o manejo pós-operatório e as opções terapêuticas para a doença metastática. Conclusões O diagnóstico de CMT deve ser suspeitado na presença de nódulo tireoidiano e história familiar de CMT e/ou associação com feocromocitoma, hiperparatireoidismo e/ou fenótipo sindrômico característico, como ganglioneuromatose e habitus marfanoides. A punção aspirativa por agulha fina do nódulo, a dosagem de calcitonina sérica e o exame anatomopatológico podem contribuir na confirmação do diagnóstico. A cirurgia é o único tratamento que oferece a possibilidade de cura. As opções de tratamento da doença metastática ainda são limitadas e restritas ao controle da doença. Uma avaliação pós-cirúrgica criteriosa para a identificação de doença residual ou recorrente é fundamental para definir o seguimento e a conduta terapêutica subsequente.

Exploring the role of technitium-99m dimercaptosuccinyl acid (V) scan in medullary carcinoma thyroid patients with postoperative persistent hypercalcitoninemia in the era of positron emission tomography-computerized tomography

Background:

Many radio-pharmaceuticals have been used over the years to localize the recurrences in patients with medullary carcinoma thyroid (MCT), including iodine-131-metaiodobenzylguanidine, thallium-201, technitium-99m dimercaptosuccinyl acid [Tc-99m DMSA (V)], Tc-99m methoxyisobutylisonitril, Tc-99 ethylenediamine diacetic acid/hydrazinonicotinyl-Tyr (3)-octreotide, and In-111 diethylenetriaminepenta-acetic acid-octreotide with varying sensitivities and specificities.

Aims:

The aim of this study is to explore the role of Tc-99m DMSA (V) scan in MCT patients with postoperative persistent hypercalcitoninemia in the positron emission tomography-computerized tomography (PET-CT) era.

Materials and Methods:

A retrospective review of 53 patients with proven sporadic MCT, who presented to our institution over a period 28 years from 1985 to 2012, was performed. Patients with persistently elevated levels of serum calcitonin (>150 pg/ml) were initially evaluated by a DMSA scan if conventional imaging failed to localize any focus of disease.

Results and Conclusions:

Our study showed that the postoperative levels of serum calcitonin significantly correlated with the overall survival of our patients and can possibly serve as a good prognostic marker. Tc-99m DMSA (V) scans demonstrated a sensitivity of 75%, specificity of 56%, a positive predictive value of 50%, and a negative predictive value of 80% in detecting metastasis in postoperative persistent hypercalcitoninemia. Our study showed that Tc-99m DMSA (V) scanning is an affordable and a reasonably sensitive imaging agent for localization of recurrent/metastatic disease. PET-CT seems to be a useful complementary tool and needs to be kept in the armamentarium for diagnosis of recurrence especially in cases of discordance between Tc-99m DMSA (V) scan and the serum calcitonin levels.

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.

Role of 18F-fluorodeoxyglucose PET in the study of neuroendocrine tumors

The most widely used PET radiopharmaceutical in daily clinical practice is (18)F-fluorodeoxyglucose (FDG). The evaluation of glycolytic metabolism by (18)F-FDG is potentially useful in identifying high-risk patients with aggressive neuroendocrine disease associated with a poor outcome. Although the use of new somatostatin analogues labeled with 68-Gallium for PET has significantly increased the sensitivity of NET imaging compared with single photon emission computed tomography and (18)F-FDG-PET, (18)F-FDG may retain an important role in managing patients with NETs owing to its high prognostic value and its higher sensitivity in delineating disease extent, especially in aggressive and high-grade tumors.

Depicting medullary thyroid cancer recurrence: the past and the future of nuclear medicine imaging

CONTEXT

Inherited and sporadic medullary thyroid cancer (MTC) is an uncommon and medically challenging malignancy. Even if the extent of initial surgery is deemed adequate, the recurrence rate remains high, up to 50% in most series. Measurement of serum calcitonin is important in the follow-up of patients with MTC, and reliably reflects the existence of the disease.

EVIDENCE ACQUISITION

There is no single sensitive diagnostic imaging method to reveal all MTC recurrences or metastases. Conventional morphologic imaging methods (U/S, CT, and MRI) and several methods of nuclear medicine have been used for this purpose with variable accuracy.

RESULTS

The main role of nuclear medicine imaging is the detection of residual or recurrent tumor in the postoperative follow-up. In this review we present the radiopharmaceuticals used in the diagnosis of MTC recurrence, and comparison among them.

CONCLUSIONS

The most used radiopharmaceuticals labelled with γ emitters are: Metaiodobenzylguanidine (MIBG), labelled with (131)I or (123)I, (111)In-pentetreotide (Octreoscan), 99mTc-pentavalent dimercaptosuccinic acid ((99m)Tc(V)-DMSA), and (99m)Tc-EDDA/HYNIC-Tyr3-Octreotide ( Tektrotyd). The radiopharmaceuticals labelled with a positron-emitting radionuclide (β+), suitable for positron emission tomography (PET) imaging are: (18)F-fluorodeoxyglucose ((18)F-FDG), (18)F-fluorodihydroxyphenylalanine (18F-DOPA), and 68Ga-labelled somatostatin analogues (68Ga-DOTATATE or DOTATOC).

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.

Treatment of advanced medullary thyroid cancer

Therapy decisions in advanced medullary thyroid carcinoma should be guided by a critical appraisal of the natural disease course (slowly progressive vs. aggressive) and benefits and side effects of therapy. Therapy goals should be distinguished between curative and palliative. Local treatments are mainly palliative and may add to quality of life. The advent of novel systemic therapies opens promising perspectives but its place in the therapeutic arsenal must be further determined.

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.

Detection rate of recurrent medullary thyroid carcinoma using fluorine-18 fluorodeoxyglucose positron emission tomography: a meta-analysis

Several studies evaluated the diagnostic performance of fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET), and positron emission tomography/computed tomography (PET/CT) in detecting recurrent medullary thyroid carcinoma (MTC) with conflicting results. Aim of our study is to meta-analyze published data about this topic. A comprehensive computer literature search of studies published in PubMed/MEDLINE, Scopus, and Embase databases through December 2011 and regarding FDG PET or PET/CT in patients with suspected recurrent MTC was carried out. Pooled detection rate (DR) on a per patient-based analysis was calculated to measure the diagnostic performance of FDG PET and PET/CT in this setting. A sub-analysis considering PET device used, serum calcitonin, carcino-embryonic antigen (CEA), calcitonin doubling time (CTDT), and CEA doubling time (CEADT) values was also performed. Twenty-four studies comprising 538 patients with suspected recurrent MTC were included. DR of FDG PET or PET/CT in suspected recurrent MTC on a per patient-based analysis was 59 % (95 % confidence interval: 54-63 %). Heterogeneity between the studies was revealed. DR increased in patients with serum calcitonin ≥ 1,000 ng/L (75 %), CEA ≥ 5 ng/ml (69 %), CTDT <12 months (76 %), and CEADT <24 months (91 %). In patients with suspected recurrent MTC FDG PET and PET/CT are associated with a non-optimal DR since about 40 % of suspected recurrent MTC remain usually unidentified. However, FDG PET and PET/CT could modify the patient management in a certain number of recurrent MTC because these methods are often performed after negative conventional imaging studies. DR of FDG PET and PET/CT increases in patients with higher calcitonin and CEA values and lower CTDT and CEADT values, suggesting that these imaging methods could be very helpful in patients with more aggressive disease.

Clinical relevance of 18F-FDG PET and 18F-DOPA PET in recurrent medullary thyroid carcinoma

The transition from stable to progressive disease is unpredictable in patients with biochemical evidence of medullary thyroid carcinoma (MTC). Calcitonin and carcinoembryonic antigen (CEA) doubling times are currently the most reliable markers for progression, but for accurate determination, serial measurements, which need time, are required. We compared (18)F-FDG PET and (18)F-dihydroxyphenylanaline ((18)F-DOPA) PET with biochemical parameters and survival to assess whether these imaging modalities could be of value in detecting progressive disease.

METHODS

We evaluated the outcome of (18)F-FDG PET or (18)F-DOPA PET with calcitonin and CEA doubling times in 47 MTC patients. A subgroup of patients was included in the whole metabolic burden (WBMTB) analysis, with determination of standardized uptake values and number of lesions. WBMTB of (18)F-DOPA PET and (18)F-FDG PET was compared with biochemical parameters. Furthermore, survival was compared with (18)F-DOPA PET or (18)F-FDG PET positivity.

RESULTS

Doubling times were available for 38 of 40 patients undergoing (18)F-FDG PET. There was a significant correlation with (18)F-FDG PET positivity. Doubling times were less than 24 mo in 77% (n = 10/13) of (18)F-FDG PET-positive patients, whereas 88% (n = 22/25) of (18)F-FDG PET-negative patients had doubling times greater than 24 mo (P < 0.001). Between doubling times and (18)F-DOPA PET positivity, no significant correlation existed. (18)F-DOPA PET detected significantly more lesions (75%, 56/75) than did (18)F-FDG PET (47%, 35/75) in the 21 patients included in WBMTB analysis (P = 0.009). Calcitonin and CEA levels correlated significantly with WBMTB on (18)F-DOPA PET, but doubling times did not. (18)F-FDG PET positivity was a more important indicator for poor survival in patients for whom both scans were obtained.

CONCLUSION

(18)F-FDG PET is superior in detecting patients with biochemical progressive disease and identifying patients with poor survival. Although (18)F-DOPA PET has less prognostic value, it can more accurately assess the extent of the disease in patients with residual MTC. Hence, both scans are informative about tumor localization and behavior. On the basis of these results, we designed a clinical flow diagram for general practice in detecting recurrent MTC.

Update on thyroid cancer treatment

Surgery and radioiodine therapy are usually effective for most patients with differentiated thyroid cancer. However, poorly differentiated and anaplastic thyroid carcinomas represent a challenge to physicians on the basis of the current cancer treatment modalities. These cancer subtypes are often lethal and refractory to radioiodine therapy as well as most of the common chemotherapy drugs. Several kinase inhibitors are promising targeted therapies for these malignancies; however, clinical trials involving these drugs have provided controversial results and their clinical use is still under debate. Advanced medullary thyroid carcinomas may also be refractory to conventional therapies and novel kinase inhibitors may also be useful to control tumor progression in certain patients. Novel evidence is emerging that thyroid cancer is a stem cell disease, thereby implying that the driving force of thyroid cancers is a subset of undifferentiated cells (thyroid cancer stem cells) with unlimited growth potential and resistance to conventional therapeutic regimens. Thyroid cancer stem cells have been proposed as responsible for tumor invasiveness, metastasis, relapse and differentiation. Therefore, drugs that selectively target these cells could serve as a cornerstone in the treatment of poorly differentiated thyroid cancer.

Detection rate of recurrent medullary thyroid carcinoma using fluorine-18 dihydroxyphenylalanine positron emission tomography: a meta-analysis

RATIONALE AND OBJECTIVES

The aim of this study was to perform a meta-analysis of published data about the diagnostic performance of (18)F-dihydroxyphenylalanine (DOPA) positron emission tomography (PET) or PET/computed tomography (CT) in detecting recurrent medullary thyroid carcinoma (MTC).

MATERIALS AND METHODS

A comprehensive literature search of studies indexed in the PubMed/MEDLINE, Scopus, and Embase databases through January 2012 and regarding (18)F-DOPA PET or PET/CT in patients with suspected recurrent MTC was carried out. Pooled detection rates (DR) in per patient and per lesion analyses were calculated. A subanalysis considering serum levels of calcitonin and carcinoembryonic antigen, device used, and carbidopa pretreatment was also performed.

RESULTS

Eight studies including 146 patients with suspected recurrent MTC were included. The DRs of (18)F-DOPA PET and PET/CT in per patient and per lesion analyses were 66% and 71%, respectively. DRs significantly increased in patients with serum calcitonin ≥1000 ng/L (86%) and calcitonin doubling times <24 months (86%).

CONCLUSIONS

Fluorine-18-DOPA PET and PET/CT may be useful functional imaging methods in detecting recurrent MTC. The DR of recurrent MTC using these imaging methods increases in patients with higher calcitonin levels and lower calcitonin doubling times.

Added value of early 18F-FDOPA PET/CT acquisition time in medullary thyroid cancer

The aim of this study was to determine whether early acquisition of F-fluorodihydroxyphenylalanine (F-FDOPA) PET/CT could improve the detection of medullary thyroid cancer (MTC). We retrospectively compared early (median time: 15 min) and delayed (median time: 94 min) acquisitions, positive on at least one of the two phases, in 15 dual-phase F-FDOPA PET/CT examinations performed on 14 patients referred for initial staging (one examination), suspected recurrence (eight examinations) or restaging of MTC (six examinations). Among the 14 true-positive (TP) examinations, more lesions (51 vs. 43) or more intense uptake (mean SUVmax=4 vs. 2.4, P<0.05) was observed on early versus delayed phases, regardless of the anatomical site of disease (lymph node, liver or bone). The only false-positive case, a reactive lymph node, was visible only on the delayed acquisition. Early acquisition appeared to be more appropriate in the detection of MTC lesions compared with acquisition at 60 min or later.

PET Imaging in Recurrent Medullary Thyroid Carcinoma

Purpose. To perform an overview about the role of positron emission tomography (PET) or PET/computed tomography (PET/CT) using different radiopharmaceuticals in recurrent medullary thyroid carcinoma (MTC) based on biochemical findings (increased tumor marker levels after primary surgery). Methods. A comprehensive literature search of studies published in PubMed/MEDLINE, Scopus, and Embase databases through February 2012 regarding PET or PET/CT in patients with recurrent MTC was performed. Results. Twenty-nine studies comprising 714 patients with suspected recurrent MTC were retrieved. Twenty-seven articles evaluated the role of fluorine-18-fluorodeoxyglucose (FDG) PET or PET/CT in recurrent MTC with conflicting results. Diagnostic accuracy of FDG-PET and PET/CT increased in MTC patients with higher calcitonin and carcinoembryonic antigen values, suggesting that these imaging methods could be very useful in patients with more advanced and aggressive disease. Eight articles evaluated the role of fluorine-18-dihydroxyphenylalanine (FDOPA) PET or PET/CT in recurrent MTC reporting promising results. Overall, FDOPA seems to be superior but complementary compared to FDG in detecting recurrent MTC. Few studies evaluating other PET tracers are also discussed. Conclusions. PET radiopharmaceuticals reflect different metabolic pathways in MTC. FDOPA seems to be the most useful PET tracer in detecting recurrent MTC based on rising levels of tumor markers. FDG may complement FDOPA in patients with more aggressive MTC.

PET/CT using ¹⁸F-FDOPA provides improved staging of carcinoid tumor patients in a Canadian setting

AIM

In Canada, staging of carcinoid tumors is largely based on computed tomography (CT) imaging sometimes complemented with somatostatin receptor scintigraphy (SRS). This study assessed the diagnostic accuracy of 6-[¹⁸F]fluoro-3,4-dihydroxyphenylalanine (¹⁸F-FDOPA) PET/CT in neuroendocrine tumors.

METHODS

We prospectively included 27 patients with either suspected carcinoid (n=6, with all prior tests negative) or with an established diagnosis of intestinal carcinoid tumor (n=21) from two Canadian treatment centers. Findings of ¹⁸F-FDOPA PET/CT were compared with SRS, CT, and combined SRS/CT using a composite reference standard comprising all available imaging, biochemistry, surgery, and follow-up data. Sensitivity was calculated per patient, per body region, and per lesion. The contribution to patient management was estimated from the feedback of attending physicians.

RESULTS

In documented carcinoid patients, ¹⁸F-FDOPA PET/CT identified disease in 20 of 21 patients (patient-based sensitivity 95%). In 56 positive regions, ¹⁸F-FDOPA PET/CT detected 53, CT detected 34, SRS detected 34, and CT+SRS detected 39 regions, leading to region-based sensitivities of 95, 61, 62, and 71%, respectively. Lesion-based sensitivities were 96, 69, 50, and 72%, respectively. In the six patients with suspected disease only, one CT scan was positive, but ¹⁸F-FDOPA PET/CT was negative for all. ¹⁸F-FDOPA PET contributed to patient management in 12/21 patients (57%).

CONCLUSION

¹⁸F-FDOPA PET/CT proved to be an excellent modality for staging of carcinoid tumor patients, with superior performance compared with currently applied methods in Canada. In patients with suspected disease with negative prior imaging investigations, ¹⁸F-FDOPA was not helpful.

Contemporary nuclear medicine imaging of neuroendocrine tumours

Neuroendocrine tumours (NETs) are rare, heterogeneous, and often hormonally active neoplasms. Nuclear medicine (NM) imaging using single photon- and positron-emitting radiopharmaceuticals allows sensitive and highly specific molecular imaging of NETs, complementary to anatomy-based techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI). Somatostatin-receptor scintigraphy is a whole-body imaging technique widely used for diagnosis, staging and restaging of NETs. The increasing availability of hybrid single-photon emission CT (SPECT)/CT cameras now offers superior accuracy for localization and functional characterization of NETs compared to traditional planar and SPECT imaging. The potential role of positron-emission tomography (PET) tracers in the functional imaging of NETs is also being increasingly recognized. In addition to 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG), newer positron-emitting radiopharmaceuticals such as (18)F-dihydroxyphenylalanine (DOPA) and (68)Ga-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) peptides, show promise for the future. This article will summarize the role of current and emerging radiopharmaceuticals in NM imaging of this rare but important group of tumours.

2012 European thyroid association guidelines for metastatic medullary thyroid cancer

Distant metastases are the main cause of death in patients with medullary thyroid cancer (MTC). These 21 recommendations focus on MTC patients with distant metastases and a detailed follow-up protocol of patients with biochemical or imaging evidence of disease, selection criteria for treatment, and treatment modalities, including local and systemic treatments based on the results of recent trials. Asymptomatic patients with low tumor burden and stable disease may benefit from local treatment modalities and can be followed up at regular intervals of time. Imaging is usually performed every 6-12 months, or at longer intervals of time depending on the doubling times of serum calcitonin and carcinoembryonic antigen levels. Patients with symptoms, large tumor burden and progression on imaging should receive systemic treatment. Indeed, major progress has recently been achieved with novel targeted therapies using kinase inhibitors directed against RET and VEGFR, but further research is needed to improve the outcome of these patients.