Value of 111In-DOTA-lanreotide and 111In-DOTA-DPhe1-Tyr3-octreotide in differentiated thyroid cancer: results of in vitro binding studies and in vivo comparison with 18F-FDG PET

Identification of Radioactive Iodine Refractory Differentiated Thyroid Cancer

Most differentiated thyroid cancer (DTC) patients have an excellent prognosis. However, about one-third of DTC patients with recurrent or metastatic disease lose the hallmark of specific iodine uptake initially or gradually and acquire radioactive iodine-refractory DTC (RAIR-DTC) with poor prognosis. Due to the potentially severe complications from unnecessarily repeated RAI therapy and encouraging progress of multiple targeted drugs for advanced RAIR-DTC patients, it has become crucial to identify RAIR-DTC early. In this review, we focus on the progress and controversies regarding the defining of RAIR-DTC, further with subsistent approaches and promising molecular nuclear medicine imaging in identifying RAIR-DTC, which may shed light on the proper management methodsof such patients.

Expression of somatostatin receptor subtype 2 and subtype 5 in thyroid malignancies

AIM

To retrospectively analyse the expression of somatostatin receptor subtypes 2 (SSTR 2) and 5 (SSTR 5) in thyroid malignancies, possibly the most relevant subtypes for targeted therapy with somatostatin peptide radioligands. In addition, findings were also correlated with the course of disease.

PATIENTS, METHODS

87 consecutive patients (59 women, 28 men) with thyroid malignancy were included; 52 had papillary carcinoma, 24 follicular carcinoma, six medullary carcinoma, two poorly differentiated carcinoma and three anaplastic carcinoma. After initial therapy 70 (80.5%) patients showed complete remission, 11 (12.6%) patients partial remission with clinical and biochemical signs of residual disease and six (6.9%) patients progressive disease. The immunohistochemical staining results of the primary malignancy for SSTR 2 and SSTR 5 were semiquantitatively assessed and correlated with various outcome parameters.

RESULTS

In 10 of 87 (11.49%) thyroid cancer samples SSTR 2 showed positive immunohistochemical expression as compared to 75 of 87 (86.20%) for SSTR 5. All SSTR 2-positive cases expressed SSTR 5. Persistent or recurrent disease was found in 17 of 87 cases (19.54%). Fifty percent (6 /12) of SSTR 5-negative patients showed persistent disease as compared to 14.7 % (11 / 75) of SSTR 5-positive patients: seven of these were exclusively SSTR 5-positive, 4 showed dual expression of SSTR 5 and SSTR 2 (p = 0.01). No case showed only SSTR 2 expression.

CONCLUSIONS

SSTR 5 was shown to be the main receptor subtype in the analysed differentiated or anaplastic thyroid malignancies, whereas SSTR 2 was found only in a small percentage. Deficient SSTR expression may indicate higher risk for persistent or recurrent disease after initial therapy. For this reason immunohistochemistry can be considered a prognostic marker which should be further validated in prospective studies.

Somatostatin receptor PET in neuroendocrine tumours: 68Ga-DOTA0,Tyr3-octreotide versus 68Ga-DOTA0-lanreotide

PURPOSE

The aim of this study was to evaluate the impact of (68)Ga-labelled DOTA(0)-lanreotide ((68)Ga-DOTA-LAN) on the diagnostic assessment of neuroendocrine tumour (NET) patients with low to moderate uptake on planar somatostatin receptor (SSTR) scintigraphy or (68)Ga-labelled DOTA(0),Tyr(3)-octreotide ((68)Ga-DOTA-TOC) positron emission tomography (PET).

METHODS

Fifty-three patients with histologically confirmed NET and clinical signs of progressive disease, who had not qualified for peptide receptor radionuclide therapy (PRRT) on planar SSTR scintigraphy or (68)Ga-DOTA-TOC PET (n = 38) due to lack of tracer uptake, underwent (68)Ga-DOTA-LAN PET to evaluate a treatment option with (90)Y-labelled lanreotide according to the MAURITIUS trial. The included patients received 150 ± 30 MBq of each radiopharmaceutical intravenously. PET scans were acquired 60-90 min after intravenous bolus injection. Image results from both PET scans were compared head to head, focusing on the intensity of tracer uptake in terms of treatment decision. CT was used for morphologic correlation of tumour lesions. To further evaluate the binding affinities of each tracer, quantitative and qualitative values were calculated for target lesions.

RESULTS

(68)Ga-DOTA-LAN and (68)Ga-DOTA-TOC both showed equivalent findings in 24/38 patients when fused PET/CT images were interpreted. The sensitivity, specificity and accuracy of (68)Ga-DOTA-LAN in comparison to CT were 0.63, 0.5 and 0.62 (n = 53; p < 0.0001) and for (68)Ga-DOTA-TOC in comparison to CT 0.78, 0.5 and 0.76 (n = 38; p < 0.013), respectively. (68)Ga-DOTA-TOC showed a significantly higher maximum standardized uptake value (SUV(max)) regarding the primary tumour in 25 patients (p < 0.003) and regarding the liver in 30 patients (p < 0.009) compared to (68)Ga-DOTA-LAN. Corresponding values of both PET scans for tumour and liver did not show any significant correlation. (68)Ga-DOTA-TOC revealed more tumour sites than (68)Ga-DOTA-LAN (106 vs 53). The tumour to background ratios for tumour and liver calculated from SUV(max) measurements were significantly higher for (68)Ga-DOTA-TOC than (68)Ga-DOTA-LAN (p < 0.02).

CONCLUSION

(68)Ga-DOTA-TOC PET imaging is an established imaging procedure for accurate staging of NET patients. (68)Ga-DOTA-LAN should only be considered as a PET tracer of second choice in patients with no pathologic tracer uptake on (68)Ga-DOTA-TOC PET. In these patients, (68)Ga-DOTA-LAN PET can provide valuable information when evaluating PRRT as the treatment option, as a broader spectrum of human SSTR subtypes can be detected.

The next generation of positron emission tomography radiopharmaceuticals in oncology

Although (18)F-fluorodeoxyglucose ((18)F-FDG) is still the most widely used positron emission tomography (PET) radiotracer, there are a few well-known limitations to its use. The last decade has seen the development of new PET probes for in vivo visualization of specific molecular targets, along with important technical advances in the production of positron-emitting radionuclides and their related labeling methods. As such, a broad range of new PET tracers are in preclinical development or have recently entered clinical trials. The topics covered in this review include labeling methods, biological targets, and the most recent preclinical or clinical data of some of the next generation of PET radiopharmaceuticals. This review, which is by no means exhaustive, has been separated into sections related to the PET radionuclide used for radiolabeling: fluorine-18, for the labeling of agents such as FACBC, FDHT, choline, and Galacto-RGD; carbon-11, for the labeling of choline; gallium-68, for the labeling of peptides such as DOTATOC and bombesin analogs; and the long-lived radionuclides iodine-124 and zirconium-89 for the labeling of monoclonal antibodies cG250, and J591 and trastuzumab, respectively.

Nuclear medicine in the management of thyroid disease

Thyroid disease management has changed little over the last 60 years and recent work suggests that the older approach remains the most effective. Treatment of benign hyperthyroidism has shown that functional imaging is essentially linked to therapy and uptake of iodine-131 ((131)I) cannot be assumed but should be tested by pre-imaging with radio-isotopes as 10% of patients may not be suitable for (131)I therapy and 1% may have a co-existent cancer. Differentiated thyroid cancer remains unique in that it is almost alone among common solid tumors in that it is routinely cured even if cannot all be removed by surgery. This is achieved in the majority of patients by a treatment introduced in the 1940s and does not involve the use of chemotherapy drugs but a simple and cheap isotope preparation; (131)I. However, in some differentiated thyroid cancers there is no accumulation of (131)I and we know this is due to the loss, or downregulation of the sodium iodide symporter gene. This has led to the development of several strategies to overcome this loss/downregulation, for example with the use of lithium or retinoids or gene treatment. However, all these approaches have yet to be proved in a randomized controlled trial. Advances in imaging especially using (18)F-fluorodeoxy-glucose PET has enabled patients with thyroid cancer to be more accurately imaged, resulting in a greater chance of cure through surgery and external-beam radiotherapy, especially if uptake of (131)I is poor. Another approach has been the idea of using radiolabeled somatostatin analogs, which are able to demonstrate uptake in the tumor and, more recently, beta-emitting isotopes have been used for therapy when other options have failed. Therefore, whilst the treatment of differentiated thyroid cancer is, to some degree, 60 years old, new methods have been proposed and are now being tested in this disease.

Concordance between results of somatostatin receptor scintigraphy with 111In-DOTA-DPhe 1-Tyr 3-octreotide and chromogranin A assay in patients with neuroendocrine tumours

PURPOSE

Somatostatin receptor scintigraphy (SRS) and chromogranin A (CgA) assay have successfully been implemented in the clinical work-up and management of neuroendocrine tumour (NET) patients. However, there is still a lack of studies comparing results in these patients. Our aim was to compare directly in NET patients SRS and CgA assay results with special regard to tumour features such as grade of malignancy, primary origin, disease extent and function.

METHODS

One hundred twenty consecutive patients with histological confirmed NETs were investigated with (111)In-DOTA-DPhe(1)-Tyr(3)-octreotide ((111)In-DOTA-TOC) SRS and CgA immunoradiometric assay. Tumours were classified by cell characteristics [well-differentiated NETs, well-differentiated neuroendocrine carcinomas, poorly differentiated neuroendocrine carcinomas (PDNECs)], primary origin (foregut, midgut, hindgut, undetermined), disease extent (limited disease, metastases, primary tumour and metastases) and functionality (secretory, nonsecretory).

RESULTS

SRS was positive in 107 (89%) patients; CgA levels were increased in 95 (79%) patients. Overall, concordance between SRS and CgA results was found in 84 patients. Positive SRS but normal CgA level were found in 24 patients, with higher prevalence (p<0.05) in patients with nonsecretory tumours. Conversely, negative SRS but CgA level increased were seen in 12 patients, with higher proportion (p<0.05) in patients with PDNECs and tumours of hindgut origin.

CONCLUSIONS

Overall, (111)In-DOTA-TOC SRS proved to be more sensitive than CgA in NETs patients. Tumour differentiation, disease extent and presence of liver metastases impact both SRS and CgA results, whereas nonsecretory activity is a negative predictor of only CgA increase. PDNECs and hindgut origin of tumours predispose to discrepancies with negative SRS but increased CgA levels.

PET (positron emission tomography) imaging of biomolecules using metal-DOTA complexes: a new collaborative challenge by chemists, biologists, and physicians for future diagnostics and exploration of in vivo dynamics

Recently, PET has been paid a great deal of attention as a non-invasive imaging method. In this review, the recent advances of PET using biomolecules, such as peptides, monoclonal antibodies, proteins, oligonucleotides, and glycoproteins will be described. So far, PET of biomolecules has been mainly used for diagnosis of cancers. The biomolecules have been conjugated with the DOTA ligand, labeled with radiometals as the beta+ emitter, and targeted to specific tumors, where they have enabled visualization of even small metastatic lesions, due to the high sensitivity of the PET scanners. Some of the biomolecules have been used not only for PET diagnosis, but also for radiotherapeutic treatments by simply changing the radiometals to beta(-) emitters. Collaborative work between chemists, biologists, and physicians will be important for the future of biomolecule-based targeting and diagnosis.

99mTc-depreotide scintigraphy versus 18F-FDG-PET in the diagnosis of radioiodine-negative thyroid cancer

BACKGROUND

Papillary and follicular thyroid cancer were found recently to express somatostatin receptors (SSTRs). (99m)Tc-depreotide binds with high affinity to SSTRs 2, 3, and 5.

AIM

The aim of this study was to evaluate the feasibility of applying (99m)Tc-depreotide scintigraphy to search for radioiodine-negative thyroid cancer; comparison is made to a standard approach using (18)F-fluorodeoxyglucose-positron emission tomography ((18)F-FDG-PET).

PATIENTS AND METHODS

Ten radioiodine-negative patients with suspicion of recurrent or metastatic thyroid cancer were investigated with (99m)Tc-depreotide scintigraphy and (18)F-FDG-PET, performed with a time interval that ranged from 1-8 wk. Locoregional recurrence and metastases were confirmed by ultrasonography and/or computed tomography, together with cytology or histological examination in selected cases.

RESULTS

True-positive results were obtained in nine patients (90%) with (99m)Tc-depreotide scintigraphy and in seven patients (70%) with (18)F-FDG-PET. (99m)Tc-depreotide scintigraphy gave better results in terms of detection of recurrent or metastatic disease compared with (18)F-FDG-PET in three patients, whereas (18)F-FDG-PET identified metastatic disease that was not seen with (99m)Tc-depreotide in only one patient. (99m)Tc-depreotide scintigraphy portrayed lesions in three patients with negative morphological imaging.

CONCLUSIONS

Results indicate a potential value of (99m)Tc-depreotide scintigraphy for the diagnosis of thyroid cancer in the setting of detectable thyroglobulin and negative radioiodine scan. Furthermore, (99m)Tc-depreotide adds complementary information regarding the SSTR status of lesions, which may be helpful for individual therapy planning in this group of patients, which is hard to manage clinically.

Comparison of 111In-DOTA-DPhe1-Tyr3-octreotide and 111In-DOTA-lanreotide scintigraphy and dosimetry in patients with neuroendocrine tumours

PURPOSE

Somatostatin receptor scintigraphy with (111)In-DOTA-D: Phe(1)-Tyr(3)-octreotide ((111)In-DOTA-TOC) and (111)In-DOTA-lanreotide ((111)In-DOTA-LAN) has been used for staging of neuroendocrine tumours (NETs). However, the comparative diagnostic value of these radioligands on a lesion basis has not yet been established. The aim of this study was to compare the diagnostic capacity of (111)In-DOTA-TOC and (111)In-DOTA-LAN scintigraphy in patients with NETs, evaluating whether significant differences exist in lesion imaging with these radioligands. Furthermore, dosimetric data were compared.

METHODS

Forty-five patients with NETs were investigated with (111)In-DOTA-TOC and (111)In-DOTA-LAN scintigraphy. Scintigraphic results were compared with those of conventional imaging and/or surgery in each patient, and also (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in 20 patients.

RESULTS

(111)In-DOTA-TOC and (111)In-DOTA-LAN scintigraphy were true positive in 42/45 (93%) and 39/45 (87%) patients, and imaged 74/91 (81%) and 73/91 (80%) tumour lesions, respectively. (111)In-DOTA-TOC and (111)In-DOTA-LAN detected liver metastases in 21 and 14 patients, mediastinal metastases in seven and 11 patients, and bone metastases in two and seven patients, respectively. These radioligands revealed lesions not seen by conventional imaging in seven and eight patients, respectively, or by (18)F-FDG-PET in eight and seven patients, respectively. The estimated tumour absorbed doses for (90)Y-DOTA-TOC were higher than those for (90)Y-DOTA-LAN in 14 patients, whereas the opposite was true in 12 patients.

CONCLUSION

Both (111)In-DOTA-TOC and (111)In-DOTA-LAN are suitable for imaging tumour lesions in patients with NETs and can detect lesions that may not be seen by conventional imaging and (18)F-FDG-PET. Compared with (111)In-DOTA-LAN, (111)In-DOTA-TOC has a superior diagnostic capacity for liver metastases, but a lower diagnostic capacity for metastatic lesions in mediastinum and bone.

Staging and treatment of differentiated thyroid carcinoma with radiolabeled somatostatin analogs

In patients with progressive metastatic (or recurrent) differentiated thyroid carcinoma that either do not take up radioiodine or are unresponsive to continued radioiodine therapy, staging is difficult and treatment options are few. However, in most of these patients uptake of radiolabeled somatostatin analogs is evident on somatostatin-receptor scintigraphy (SRS). Using SRS, patients with sufficient uptake of radiolabeled somatostatin analogs can be selected for high-dose peptide receptor radionuclide therapy (PRRT) as an alternative targeted-treatment option. PRRT with the beta-particle-emitting radionuclides (90)yttrium ((90)Y) and (177)lutetium ((177)Lu) gives the best results in terms of objective tumor response. Promising, novel, radiolabeled somatostatin analogs that have a broader receptor affinity profile and, thus, a potentially wider therapeutic range are being tested clinically.