Anti-carcinoembryonic antigen antibodies versus somatostatin analogs in the detection of metastatic medullary thyroid carcinoma: are carcinoembryonic antigen and somatostatin receptor expression prognostic factors?

Current Status of Radiopharmaceuticals for the Theranostics of Neuroendocrine Neoplasms

Nuclear medicine plays a pivotal role in the management of patients affected by neuroendocrine neoplasms (NENs). Radiolabeled somatostatin receptor analogs are by far the most advanced radiopharmaceuticals for diagnosis and therapy (radiotheranostics) of NENs. Their clinical success emerged receptor-targeted radiolabeled peptides as an important class of radiopharmaceuticals and it paved the way for the investigation of other radioligand-receptor systems. Besides the somatostatin receptors (sstr), other receptors have also been linked to NENs and quite a number of potential radiolabeled peptides have been derived from them. The Glucagon-Like Peptide-1 Receptor (GLP-1R) is highly expressed in benign insulinomas, the Cholecystokinin 2 (CCK2)/Gastrin receptor is expressed in different NENs, in particular medullary thyroid cancer, and the Glucose-dependent Insulinotropic Polypeptide (GIP) receptor was found to be expressed in gastrointestinal and bronchial NENs, where interestingly, it is present in most of the sstr-negative and GLP-1R-negative NENs. Also in the field of sstr targeting new discoveries brought into light an alternative approach with the use of radiolabeled somatostatin receptor antagonists, instead of the clinically used agonists. The purpose of this review is to present the current status and the most innovative strategies for the diagnosis and treatment (theranostics) of neuroendocrine neoplasms using a cadre of radiolabeled regulatory peptides targeting their receptors.

Arriving at the Right Diagnosis in an Era of Precision Medicine

In the era of precision medicine and targeted therapy, diagnostic inaccuracy can have tremendous ramifications. We present the case of a 61-year-old man initially diagnosed with small cell lung cancer by pathology. Prior to initiating chemotherapy, multidisciplinary discussions led to an amendment of the diagnosis to medullary thyroid cancer.

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.

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 18F-DOPA, 18F-FDG and 68Ga-somatostatin analogue PET/CT in patients with recurrent medullary thyroid carcinoma

PURPOSE

To retrospectively evaluate and compare (18)F-FDG, (18)F-DOPA and (68)Ga-somatostatin analogues for PET/CT in patients with residual/recurrent medullary thyroid carcinoma (MTC) suspected on the basis of elevated serum calcitonin levels.

METHODS

Included in the study were 18 patients with recurrent MTC in whom functional imaging with the three tracers was performed. The PET/CT results were compared on a per-patient basis and on a per-lesion-basis.

RESULTS

At least one focus of abnormal uptake was observed on PET/CT in 13 patients with (18)F-DOPA (72.2% sensitivity), in 6 patients with (68)Ga-somatostatin analogues (33.3%) and in 3 patients with (18)F-FDG (16.7%) (p < 0.01). There was a statistically significant difference in sensitivity between (18)F-DOPA and (18)F-FDG PET/CT (p < 0.01) and between (18)F-DOPA and (68)Ga-somatostatin analogue PET/CT (p = 0.04). Overall, 72 lesions were identified on PET/CT with the three tracers. (18)F-DOPA PET/CT detected 85% of lesions (61 of 72), (68)Ga-somatostatin analogue PET/CT 20% (14 of 72) and (18)F-FDG PET/CT 28% (20 of 72). There was a statistically significant difference in the number of lymph node, liver and bone lesions detected with the three tracers (p < 0.01). In particular, post-hoc tests showed a significant difference in the number of lymph node, liver and bone lesions detected by (18)F-DOPA PET/CT and (18)F-FDG PET/CT (p < 0.01 for all the analyses) and by (18)F-DOPA PET/CT and (68)Ga-somatostatin analogue PET/CT (p < 0.01 for all the analyses). The PET/CT results led to a change in management of eight patients (44%).

CONCLUSION

(18)F-DOPA PET/CT seems to be the most useful imaging method for detecting recurrent MTC lesions in patients with elevated serum calcitonin levels, performing better than (18)F-FDG and (68)Ga-somatostatin analogue PET/CT. (18)F-FDG may complement (18)F-DOPA in patients with an aggressive tumour.

A review on the clinical uses of SPECT/CT

In the era when positron emission tomography (PET) seems to constitute the most advanced application of nuclear medicine imaging, still the conventional procedure of single photon emission computed tomography (SPECT) is far from being obsolete, especially if combined with computed tomography (CT). In fact, this dual modality imaging technique (SPECT/CT) lends itself to a wide variety of useful diagnostic applications whose clinical impact is in most instances already well established, while the evidence is growing for newer applications. The increasing availability of new hybrid SPECT/CT devices with advanced technology offers the opportunity to shorten acquisition time and to provide accurate attenuation correction and fusion imaging. In this review we analyse and discuss the capabilities of SPECT/CT for improving sensitivity and specificity in the imaging of both oncological and non-oncological diseases. The main advantages of SPECT/CT are represented by better attenuation correction, increased specificity, and accurate depiction of the localization of disease and of possible involvement of adjacent tissues. Endocrine and neuroendocrine tumours are accurately localized and characterized by SPECT/CT, as also are solitary pulmonary nodules and lung cancers, brain tumours, lymphoma, prostate cancer, malignant and benign bone lesions, and infection. Furthermore, hybrid SPECT/CT imaging is especially suited to support the increasing applications of minimally invasive surgery, as well as to precisely define the diagnostic and prognostic profile of cardiovascular patients. Finally, the applications of SPECT/CT to other clinical disorders or malignant tumours is currently under extensive investigation, with encouraging results in terms of diagnostic accuracy.

Molecular imaging in thyroid cancer

Molecular imaging plays an important role in the evaluation and management of thyroid cancer. The routine use of thyroid scanning in all thyroid nodules is no longer recommended by many authorities. In the initial work-up of a thyroid nodule, radioiodine imaging can be particularly helpful when the thyroid stimulating hormone level is low and an autonomously functioning nodule is suspected. Radioiodine imaging can also be helpful in the 10–15% of cases for which fine-needle aspiration biopsy is indeterminate. Therapy of confirmed thyroid cancer frequently involves administration of iodine-131 after surgery to ablate remnant tissue. In the follow-up of thyroid cancer patients, increased thyroglobulin levels will often prompt the empiric administration of ¹³¹I followed by whole body radioiodine imaging in the search for recurrent or metastatic disease. ¹³¹I imaging of the whole body and blood pharmacokinetics can be used to determine if higher doses of ¹³¹I can be given in thyroid cancer. The utility of [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET) is steadily increasing. FDG is primarily taken up by dedifferentiated thyroid cancer cells, which are poorly iodine avid. Thus, it is particularly helpful in the patient with an increased thyroglobulin but negative radioiodine scan. FDG PET is also useful in the patient with a neck mass but unknown primary, in patients with aggressive (dedifferentiated) thyroid cancer, and in patients with differentiated cancer where histologic transformation to dedifferentiation is suspected. In rarer types of thyroid cancer, such as medullary thyroid cancer, FDG and other tracers such as ^99mTc sestamibi, [¹¹C]methionine, [¹¹¹In]octreotide, and [⁶⁸Ga]somatostatin receptor binding reagents have been utilized. ¹²⁴I is not widely available, but has been used for PET imaging of thyroid cancer and will likely see broader applicability due to the advantages of PET methodology.

Nuclear medicine procedures in the diagnosis and therapy of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor originating in the parafollicular cells (C cells) of the thyroid and secretes both calcitonin and carcino-embryonic antigen (CEA). Genetic and biochemical testing allow early pre-clinical identification of familial forms. Sporadic MTC usually presents as a solitary thyroid nodule; the diagnosis can be made preoperatively by fine-needle aspiration or by calcitonin assay, though it is usually established at the time of surgery. In the diagnostic assessment of MTC, nuclear medicine imaging provides its contribution mainly in the post-operative work-up to detect residual/recurrent tumor. For such purpose a number of radiopharmaceuticals, which take advantage of the specific expression of receptors (the somatostatin analogue (111)In-octreotide), hormone transporters (radiolabelled MIBG) or molecular targets (radiolabelled anti-CEA monoclonal antibodies) by MTC lesions are available; these tracers may be used also for the palliative treatment of advanced MTC. Interesting perspectives for MTC imaging are offered by PET radiopharmaceuticals.

Somatostatin receptor scintigraphy using 99mTc-EDDA/HYNIC-TOC in patients with medullary thyroid carcinoma

PURPOSE

Several new somatostatin analogues have been developed for the diagnosis and therapy of different tumours. Since somatostatin receptors are often over-expressed in medullary thyroid carcinoma (MTC), the aim of our study was to evaluate the utility of scintigraphy with the somatostatin analogue (99m)Tc-EDDA/HYNIC-TOC in MTC in comparison with other diagnostic techniques.

METHODS

Forty-five patients with MTC, aged 14-83 years, were investigated. Scintigraphy using (99m)Tc-EDDA/HYNIC-TOC (Tektrotyd) was performed 2 and 4 h post injection of 740 MBq (20 mCi) of the tracer. Other imaging techniques were also applied and analysed in individual cases (ultrasonography, computed tomography, (99m)Tc(V)-DMSA, (131)I-MIBG, (99m)Tc-MDP, (111)In-DTPA-octreotide and (18)F-FDG-PET) and compared with (99m)Tc-EDDA/HYNIC-TOC.

RESULTS

In group 1 (eight patients before thyroidectomy), uptake of the tracer was found in the primary tumours. In group 2 (six patients with remission), a false positive result was found in one patient; in the remaining five patients, no pathological foci were visualised. In group 3 (31 patients with post-surgical hypercalcitoninaemia), scintigraphy was true positive in 23 patients (74.2%): uptake in the thyroid bed was found in five patients, in the lymph nodes in 18 and in bone metastases in four. Using (99m)Tc-EDDA/HYNIC-TOC scintigraphy, the overall sensitivity was 79.5%, specificity 83.3%, accuracy 80.0%, positive predictive value 96.9% and negative predictive value 38.5%.

CONCLUSION

(99m)Tc-EDDA/HYNIC-TOC is clinically useful for scintigraphy in the follow-up of patients with MTC. It can be used in clinical practice for preoperative evaluation, for localisation of local recurrence or distant metastases and particularly for therapy decision making.

Nuclear medicine imaging and therapy of neuroendocrine tumours

Radiolabelled peptides are used for specific targeting of receptors (over-)expressed by tumour cells. Dependent on the kind of labelling and the radionuclide used, these compounds may be utilised for imaging or for therapy. A concise overview is provided on basic principles of designing and developing radiopeptides for these applications. Furthermore, clinical application of these compounds for imaging and therapy is described. Advantages of the method compared to other techniques (such as the use of radiolabelled antibodies or antibody fragments) are discussed as well as pitfalls and limitations.

Improved tumour detection by gastrin receptor scintigraphy in patients with metastasised medullary thyroid carcinoma

PURPOSE

Radiopeptide imaging is a valuable imaging method in the management of patients with neuroendocrine tumours (NET). To determine the clinical performance of gastrin receptor scintigraphy (GRS), it was compared with somatostatin receptor scintigraphy (SRS), computed tomography (CT) and (18)F-FDG positron emission tomography (PET) in patients with metastasised/recurrent medullary thyroid carcinoma (MTC).

METHODS

Twenty-seven consecutive patients underwent imaging with GRS, SRS (19 patients), CT and PET (26 patients). GRS and SRS were compared with respect to tumour detection and uptake. CT, PET, magnetic resonance imaging (MRI), ultrasound (US) and follow-up were used for verification of findings. In addition, GRS, CT and PET were directly compared with each other to determine which method performs best.

RESULTS

Nineteen patients underwent both GRS and SRS. Among these, GRS showed a tumour detection rate of 94.2% as compared to 40.7% for SRS [mean number of tumour sites (+/-SD) and 95% confidence intervals (CI): GRS 4.3+/-3.1/2.8-5.7, SRS 1.8+/-1.6/1.1-2.6]. In 26 patients, GRS, CT and PET were compared. Here, GRS showed a tumour detection rate of 87.3% (CT 76.1%, PET 67.2%; mean number of tumour sites and 95% CI: GRS 4.5+/-4.0/2.9-6.1, CT 3.9+/-3.5/2.5-5.3, PET 3.5+/-3.3/2.1-4.8). If GRS and CT were combined, they were able to detect 96.7% of areas of tumour involvement.

CONCLUSION

GRS had a higher tumour detection rate than SRS and PET in our study. GRS in combination with CT was most effective in the detection of metastatic MTC.

Angiography-proven liver metastases explain low efficacy of lymph node dissections in medullary thyroid cancer patients

AIM

To report the role of liver angiography in the staging of medullary thyroid cancer (MTC) patients.

MATERIAL AND METHODS

Sixty MTC patients with persistent or recurrent hypercalcitonemia (n=49), a characteristic general symptom (diarrhea, n=4) or a normal basal calcitonin level without general symptoms (n=7) were investigated by dynamic liver CT, MRI and angiography between 06/1998 and 06/2002.

RESULTS

Dual-phase CT and MRI investigations identified hepatic metastases with relatively low frequency (8/58 on MRI, and 7/60 on CT). Angiography indicated liver involvement in 54/60 cases. The hepatic metastases were typically multiple, hypervascular, small foci (only 13 foci measured >/=10 mm). With one exception significant disease progression was not observed over 5 years of follow-up.

CONCLUSIONS

Liver angiography is a powerful tool to reveal hepatic metastases in MTC patients. Frequent, inoperable liver metastases in hypercalcitoninemic MTC patients demonstrate that secondary lymph node dissection is an inefficient technique for restoration of a normal calcitonin level.