Search

Background/Objectives: Myocarditis is an inflammatory disease of the myocardium and remains to this day a challenging diagnosis. A promising novel imaging method uses the expression of somatostatin receptors (SSTRs) on inflammatory cells to visualize myocardial inflammation. However, little is known about the histopathological correlate of SSTR imaging in different forms of myocarditis. Methods: In the present retrospective histopathological study, we systematically analysed the expression of SSTR subtype 2 (SSTR2) on inflammatory cells of 33 patients with biopsy- or explant-proven myocarditis (lymphocytic myocarditis (n = 5), giant-cell myocarditis (n = 11), and cardiac sarcoidosis (n = 17)), and in eight controls (multi-organ donors) without signs of myocardial inflammation and/or scars. Results: In all patients, immunohistochemical staining for SSTR2 was positive in areas with CD68-positive macrophages and multinucleated giant cells. Staining for SSTR2 was most prominent in the presence of multinucleated giant cells. The colocalization of both SSTR2 and CD68 on the same cell could be confirmed using immunofluorescence microscopy. Western blotting confirmed the upregulated expression of SSTR2 in cases of granulomatous inflammation (sarcoidosis) of the skeletal and heart muscle, in comparison with controls. Conclusions: In conclusion, our findings demonstrate the expression of SSTR2 on the protein level on CD68-positive macrophages and multinucleated giant cells in various forms of myocarditis, which provides a clear rationale for the diagnostic use of SSTR imaging in this patient group. [ABSTRACT FROM AUTHOR]

Introduction: Neuroendocrine neoplasms encompass well-differentiated tumors (NETs) and poorly differentiated carcinomas (neuroendocrine carcinomas [NECs]), which are distinguished by their clinical behavior and molecular characteristics. They can cause paraneoplastic syndromes, such as ectopic adrenocorticotropic hormone (ACTH)-dependent Cushing’s syndrome (CS), necessitating prompt recognition and management due to severe hypercortisolism. Case Presentation: A 66-year-old patient with a 3-year history of metastatic mixed neuroendocrine-non-neuroendocrine neoplasm with a NEC and adenocarcinoma component originating from the vulva presented to the emergency department with dyspnea and fatigue. Upon clinical examination, we found widespread hyperpigmentation, a moon-face appearance, hirsutism, buffalo hump, and muscle atrophy. Laboratory investigations revealed severe hypokalemia (2.3 mmol/L), elevated serum cortisol (1,726 nmol/L) and ACTH (194 ng/L) levels. Urinary free cortisol measurement was 21-fold the upper limit of the reference range (3,614.0 nmol/24 h), and cortisol concentration did not decrease after 1mg-dexamethasone suppression test (1,812 nmol/L for an expected value <50 nmol/L), confirming the ACTH-dependent CS. Thoracoabdominal computed tomography (CT) scan demonstrated progressive neoplastic disease in the liver, kidney, lymph nodes, peritoneum, and lungs. Brain magnetic resonance imaging indicated multifocal metastatic infiltration but no evidence of pituitary adenoma. Interestingly, despite a previously negative 68Ga-DOTATATE positron emission tomography (PET)/CT performed 1 year prior, there was moderate somatostatin receptor (SSTR) expression in lymphatic, pulmonary, peritoneal, and bone tissues, suggesting the presence of a component with redifferentiation and re-expression of the SSTR. After the workup, the patient was admitted to a supportive care facility. Hypercortisolism symptoms were effectively managed with an adrenal enzyme inhibitor (ketoconazole) in combination with somatostatin analogs. Unfortunately, the patient was too frail to benefit from peptide receptor radionuclide therapy (PRRT). Conclusion: This redifferentiation phenomenon in neuroendocrine tumors should be further investigated as patients might be, under certain conditions, eligible for PRRT. Therefore, we suggest that newly occurring paraneoplastic syndromes in patients with NEC should always be evaluated using 68Ga-DOTATATE PET/CT. [ABSTRACT FROM AUTHOR]

Purpose: 18F-labelled somatostatin receptor (SSTR) analogs offer several advantages over 68Ga in terms of yield, cost, spatial resolution and detection rate. This study presents an interim analysis of a prospective trial designed to assess the safety, biodistribution and dosimetry of [18F]AlF-NOTA-LM3, and compare its diagnostic efficacy and clinical management outcomes with [68Ga]Ga-DOTATATE or [68Ga]Ga-NODAGA-LM3 in patients with well-differentiated NETs. Methods: Twenty-one patients with histologically confirmed well-differentiated neuroendocrine tumors (G1 and G2) were prospectively recruited. The first eight patients underwent serial PET scans at 5, 15, 30, 45, 60, and 120 min after [18F]AlF-NOTA-LM3 injection to assess biodistribution and dosimetry. The remaining patients underwent whole-body PET/CT scans. [18F]AlF-NOTA-LM3 and [68Ga]Ga-DOTATATE PET/CT were done within a week, with a minimum 24-hour interval between the two scans. Focal uptake above the surrounding background activity and could not be explained by physiologic uptake was considered lesions of NETs. Lesion number, tumor uptake, and tumor-to-background ratio (TBR) were compared. In patients with discrepant findings, the size of the smallest lesions (measured on coregistered CT) detected on [68Ga]Ga-DOTATATE and [18F]AlF-NOTA-LM3 was compared. Results: [18F]AlF-NOTA-LM3 was safe and well-tolerated. Physiological uptake of [18F]AlF-NOTA-LM3 was significantly lower than that of [68Ga]Ga-DOTATATE in abdominal organs and bone marrow, but higher in blood pool and lung. The mean effective dose was 0.024 ± 0.014 mSv/MBq. [18F]AlF-NOTA-LM3 detected significantly more liver lesions (457 vs. 291, P = 0.006) and lymph node lesions (30 vs. 22, P = 0.011) compared to [68Ga]Ga-DOTATATE. The tumor uptake was comparable, but TBR was significantly higher with [18F]AlF-NOTA-LM3 for lesions from all sites except for the duodenum. The size of the minimum liver lesions (0.54 ± 0.15 vs. 1.01 ± 0.49, P<0.001) and lymph node lesions (0.50 ± 0.19 vs. 1.26 ± 0.86, P = 0.024) detected on [18F]ALF-NOTA-LM3 were significantly smaller than those detected on [68Ga]Ga-DOTATATE. Conclusion: [18F]AlF-NOTA-LM3 shows favorable biodistribution, higher spatial resolution and superior performance than [68Ga]Ga-DOTATATE in detecting liver and lymph node metastases, with higher TBR. Notably, it is the first SSTR analog to show superiority in detecting lymph node lesions when compared to [68Ga]Ga-DOTATATE. Trial registration: ClinicalTrials.gov identifier NCT06056362. [ABSTRACT FROM AUTHOR]

Purpose: To provide practice guideline/procedure standards for diagnostics and therapy (theranostics) of meningiomas using radiolabeled somatostatin receptor (SSTR) ligands. Methods: This joint practice guideline/procedure standard was collaboratively developed by the European Association of Nuclear Medicine (EANM), the Society of Nuclear Medicine and Molecular Imaging (SNMMI), the European Association of Neurooncology (EANO), and the PET task force of the Response Assessment in Neurooncology Working Group (PET/RANO). Results: Positron emission tomography (PET) using somatostatin receptor (SSTR) ligands can detect meningioma tissue with high sensitivity and specificity and may provide clinically relevant information beyond that obtained from structural magnetic resonance imaging (MRI) or computed tomography (CT) imaging alone. SSTR-directed PET imaging can be particularly useful for differential diagnosis, delineation of meningioma extent, detection of osseous involvement, and the differentiation between posttherapeutic scar tissue and tumour recurrence. Moreover, SSTR-peptide receptor radionuclide therapy (PRRT) is an emerging investigational treatment approach for meningioma. Conclusion: These practice guidelines will define procedure standards for the application of PET imaging in patients with meningiomas and related SSTR-targeted PRRTs in routine practice and clinical trials and will help to harmonize data acquisition and interpretation across centers, facilitate comparability of studies, and to collect larger databases. The current document provides additional information to the evidence-based recommendations from the PET/RANO Working Group regarding the utilization of PET imaging in meningiomas Galldiks (Neuro Oncol. 2017;19(12):1576–87). The information provided should be considered in the context of local conditions and regulations. [ABSTRACT FROM AUTHOR]

Introduction: Imaging with [68Ga]Ga-DOTA-TATE, [68Ga]Ga-DOTA-JR11, and [18F]AlF-NOTA-JR11 was performed to analyze differences among the three probes and to analyze the correlation between the image and pathology parameters. Method: Tumor-bearing mice with different positive rates of somatostatin receptor II (SSTR2) were established with HEK293-SSTR2 and HEK293 cells, and imaging was performed on the same mouse with [68Ga]Ga-DOTA-TATE, [68Ga]Ga-DOTA-JR11, and [18F]AlF-NOTA-JR11 at 20, 60, and 120 min. The image parameters were obtained, including the maximum standard uptake value (SUVmax), mean standard uptake value (SUVmean), standard deviation of SUVmean, tumor volume, and coefficient of variation (CoV). Immunohistochemistry (IHC) of the tumor was performed after imaging to obtain positive rate of SSTR2. Statistical analysis was performed to analyze the differences among the three imaging techniques and the correlations between the relative imaging parameter and IHC. Result: The SUVmax of [18F]AlF-NOTA-JR11 at 20 min and 60 min was higher than that of [68Ga]Ga-DOTA-TATE (p = 0.0015, 0.0035) and [68Ga]Ga-DOTA-JR11 (p = 0.033, 0.019), and no significant difference was found in the other groups (p > 0.05). There was a significant positive correlation between the positive rate and SUVmean of tumors with three tracers (p < 0.05). However, a significant negative correlation between the positive rate and CoV was found only in the [68Ga]Ga-DOTA-TATE group at 60 min and 120 min (p = 0.048, 0.026). Conclusion: [18F]AlF-NOTA-JR11 is more suitable for SSTR imaging within an hour than other two tracers. SUVmean of whole tumor can become an indicator for evaluating the positive rate of IHC, and the higher SUVmean of three tracers means a higher positive rate. However, the CoV is not applicable to the two antagonist tracers for evaluating the positive rate. [ABSTRACT FROM AUTHOR]

Introduction: Neuroendocrine neoplasms encompass well-differentiated tumors (NETs) and poorly differentiated carcinomas (neuroendocrine carcinomas [NECs]), which are distinguished by their clinical behavior and molecular characteristics. They can cause paraneoplastic syndromes, such as ectopic adrenocorticotropic hormone (ACTH)-dependent Cushing’s syndrome (CS), necessitating prompt recognition and management due to severe hypercortisolism. Case Presentation: A 66-year-old patient with a 3-year history of metastatic mixed neuroendocrine-non-neuroendocrine neoplasm with a NEC and adenocarcinoma component originating from the vulva presented to the emergency department with dyspnea and fatigue. Upon clinical examination, we found widespread hyperpigmentation, a moon-face appearance, hirsutism, buffalo hump, and muscle atrophy. Laboratory investigations revealed severe hypokalemia (2.3 mmol/L), elevated serum cortisol (1,726 nmol/L) and ACTH (194 ng/L) levels. Urinary free cortisol measurement was 21-fold the upper limit of the reference range (3,614.0 nmol/24 h), and cortisol concentration did not decrease after 1mg-dexamethasone suppression test (1,812 nmol/L for an expected value

[18F]AlF‐NOTA‐octreotide ([18F]AlF‐OC) is a promising alternative for [68Ga]Ga‐DOTA‐somatostatin analogs (SSAs) in positron emission tomography (PET) imaging of the somatostatin receptor (SSTR). Our aim is to assess changes in TNM staging and differences in patient management between [18F]AlF‐OC PET/CT and [68Ga]Ga‐DOTA‐SSA PET/CT in the work‐up of neuroendocrine tumor (NET) patients. Patients who underwent both [18F]AlF‐OC and [68Ga]Ga‐DOTA‐TATE or [68Ga]Ga‐DOTA‐NOC PET/CT in our multicenter study (Pauwels et al., J Nucl Med.2023;63:632–638) with a NET were included for analysis. TNM staging was determined and compared for both tracers. For each patient, the blinded [68Ga]Ga‐DOTA‐SSA or [18F]AlF‐OC PET/CT images were presented in random order at a multidisciplinary team board. The images were presented together with clinical information and compared with previous SSTR and [18F]FDG PET/CT imaging. After a consensus decision for patient management was recorded, the board was presented with the PET/CT images from the other SSTR tracer and a decision was made for the second tracer. Differences in management were classified as major if it entailed an intermodality change and minor if it led to an intramodality change. Compared with [68Ga]Ga‐DOTA‐SSA, the use of [18F]AlF‐OC led to a change in 16/75 patients: TNM staging changes in 10/75 patients (13.3%; downstaging in 3/10, upstaging in 7/10) and differences in clinical management were seen in 10/75 patients (13.3%), leading to a major difference in 7/10 cases and a minor change in 3/10 cases. All 10 cases with a difference in patient management between both PET tracers were caused by additional lesion detection by [18F]AlF‐OC. The use of [18F]AlF‐OC did not impact TNM staging or clinical management in the large majority of the patients (86.7%), further validating the potential for routine clinical use of [18F]AlF‐OC PET/CT as an alternative for [68Ga]Ga‐DOTA‐SSA PET/CT. The trial is registered under ClinicalTrials.gov identifier NCT04552847 and EudraCT 2020–000549‐15. [ABSTRACT FROM AUTHOR]

Introduction: The rise in thyroid cancer incidence, especially papillary thyroid cancer (PTC), has underscored the need for improved diagnostic methods and management strategies. Herein, we aim to comprehensively review the evolving landscape in thyroid cancer diagnosis and the potential utility of Gallium-68 (Ga-68) based somatostatin receptor imaging. Methods: We reviewed the clinical studies involving Ga-68 based radiotracers by looking at the following literature databases -PUBMED, EMBASE, WEB OF SCIENCE and COCHRANE. We employed a detailed search strategy with the following search terms; PubMed: ("gallium Ga 68 dotatate" [Supplementary Concept]) AND ("Thyroid Gland"[Mesh] OR "Thyroid Nodule"[Mesh] OR "Thyroid Neoplasms"[Mesh]), Embase ("gallium 68" AND "Thyroid Disease"), Web of Science: ("Gallium 68 and Thyroid"). Results: A comparison between Ga-68 DOTATATE and Ga-68 DOTANOC showed similar sensitivities but a higher uptake for Ga-68 DOTATATE. Studies comparing Ga-68-based SSTR PET with FDG PET highlighted the potential advantages of both approaches, with Ga-68-based SSTR PET being more specific in certain cases. Discussion: Ga-68-based somatostatin receptor imaging displays clinical utility in RAI-R DTC, offering valuable insight into detecting skeletal lymph node metastases. Notably, it shows potential as a primary imaging tool, potentially augmenting the role of FDG PET. However, SSTR PET imaging's efficacy in distinguishing benign from malignant thyroid nodules varies, with a complex interplay of factors influencing its specificity, indicating its value as an adjunct to existing methods, warranting further research for a refined role in thyroid cancer management. Conclusion: Although study variations exist, Ga-based somatostatin receptor imaging holds potential as a complementary tool alongside diagnostic methods in thyroid cancer diagnosis, with particular relevance to RAI-R DTC. In carefully selected patients demonstrating the presence of Ga-68 DOTATATE avid lesions, further exploration, and investigation into the potential utilization of Lu177 DOTATATE are warranted. [ABSTRACT FROM AUTHOR]

Objectives: The standard treatment for canine and feline meningiomas includes radiotherapy, surgical excision or combined therapy. However, new therapeutic approaches are required due to the possible recurrence or progression of meningiomas despite initial therapy. Adjunctive therapy with synthetic long‐acting somatostatin (SST) analogues has been described in humans with SST‐expressing tumours. The expression of SST receptors (SSTRs) by feline meningiomas is currently unknown, and there are little data about canine meningiomas. We hypothesized that SSTR is expressed by canine and feline meningiomas (S1). Methods: Seven canines and 11 felines with histologically confirmed meningiomas underwent STTR screening. RNA expressions of SSTR1, SSTR2, SSTR3 and SSTR5 (canine) and SSTR1–SSTR 5 (feline) in fresh frozen and formalin‐fixed and paraffin‐embedded (FFPE) samples were investigated using real‐time (RT)‐qPCR. The expression of SSTR1 and SSTR2 in FFPE samples was evaluated using immunohistochemistry (IHC). The specificity of applied antibodies for canine and feline species was confirmed by western blotting. Results: In canine meningiomas (n = 7), RNA expression of SSTR1, SSTR2 and SSTR5 was detected in all samples; SSTR3 RNA expression was detected in only 33% of samples. In feline meningiomas (n = 12), RNA expression of SSTR1, SSTR4, SSTR5 and SSTR2 was detected in 91%, 46%, 46% and 36% of samples, respectively; SSTR3 was not expressed. Overall, the detection rate was lower in FFPE samples. IHC revealed the expression of SSTR1 and SSTR2 in all samples from both species. However, it is important to exercise caution when interpreting IHC results due to the presence of diffuse background staining. Conclusions: SSTRs are widely expressed in canine and feline meningiomas, thereby encouraging further studies investigating SSTR expression to conduct trials about the effect of adjunctive therapy with long‐acting SST‐analogues. [ABSTRACT FROM AUTHOR]

Simple Summary: Metastatic pheochromocytomas and paragangliomas (PPGLs) are rare endocrine malignancies with limited effective treatment options. The association between the tumor microenvironment with somatostatin receptor 2 (SSTR2) and hypoxia-induced factor-2α (HIF-2α) in PPGLs, critical for optimizing combination therapeutic strategies with immunotherapy, remains largely unexplored. We found associations between tumor-associated macrophages and SSTR2A expression, and between PD-L1 and HIF-2α expression. Our data suggests the potential of combination therapy with immunotherapy and peptide receptor radionuclide therapy or HIF-2α inhibitors as a treatment option in selected PPGL populations. Metastatic pheochromocytomas and paragangliomas (PPGLs) are rare endocrine malignancies with limited effective treatment options. The association between the tumor microenvironment (TME) with somatostatin receptor 2 (SSTR2) and hypoxia-induced factor-2α (HIF-2α) in PPGLs, critical for optimizing combination therapeutic strategies with immunotherapy, remains largely unexplored. To evaluate the association of SSTR2 and HIF-2α immunoreactivity with the TME in patients with PPGLs, we analyzed the expression of SSTR2A, HIF-2α, and TME components, including tumor-infiltrating lymphocytes (CD4 and CD8), tumor-associated macrophages (CD68 and CD163), and PD-L1, using immunohistochemistry in patients with PPGLs. The primary outcome was to determine the association of the immune profiles with SSTR2A and HIF-2α expression. Among 45 patients with PPGLs, SSTR2A and HIF2α were positively expressed in 21 (46.7%) and 14 (31.1%) patients, respectively. The median PD-L1 immunohistochemical score (IHS) was 2.0 (interquartile range: 0–30.0). Positive correlations were observed between CD4, CD8, CD68, and CD163 levels. A negative correlation was found between the CD163/CD68 ratio (an indicator of M2 polarization) and SSTR2A expression (r = −0.385, p = 0.006). HIF-2α expression showed a positive correlation with PD-L1 IHS (r = 0.348, p = 0.013). The co-expression of PD-L1 (HIS > 10) and HIF-2α was found in seven patients (15.6%). No associations were observed between SDHB staining results and the CD163/CD68 ratio, PD-L1, or SSTR2A expression. Our data suggest the potential of combination therapy with immunotherapy and peptide receptor radionuclide therapy or HIF-2α inhibitors as a treatment option in selected PPGL populations. [ABSTRACT FROM AUTHOR]

A dopamine agonist administered for prolactinoma treatment and pituitary stimulation tests are reported as risk factors for pituitary apoplexy. We report a case of an 82‐year‐old patient who suffered from pituitary apoplexy in an endocrinologically silent adenoma during lanreotide administration. The patient was diagnosed with a pancreatic neuroendocrine tumor with lymph node metastasis and treated with lanreotide for two years. An endoscopic endonasal transsphenoidal approach was used for tumor and hematoma removal. The specimen showed growth hormone and prolactin positivity and was diagnosed as pit1‐lineage plurihormonal adenoma. The tumor also showed positivity for somatostatin receptor 2. Thus, lanreotide treatment is a risk factor for pituitary apoplexy even in silent adenoma. [ABSTRACT FROM AUTHOR]

68Ga-DOTA-TATE and 177Lu-DOTA-TATE are radiolabeled somatostatin analogs used to detect or treat neuroendocrine tumors. They are administered separately for either diagnostic or therapeutic purposes but little experimental data for their biokinetics are measured simultaneously in the same biological model. By co-administering 68Ga-DOTA-TATE and 177Lu-DOTA-TATE in three laboratory mice bearing two IMR32 tumor xenografts expressing different levels of somatostatin receptors (SSTRs) on their shoulders and imaging both 68Ga and 177Lu simultaneously, we investigated the relationship between the uptake of 68Ga-DOTA-TATE and 177Lu-DOTA-TATE in organs and tumors. In addition, using the percent of injected activity (%IA) values of 68Ga-DOTA-TATE at 0 hr and 4 hr, we investigated the correlation between 68Ga-DOTA-TATE %IA and the time-integrated activity coefficients (TIACs) of 177Lu-DOTA-TATE to estimate the organ-based and tumor-based doses of 177Lu-DOTA-TATE. The results showed that the extrapolated clearance time of 68Ga-DOTA-TATE linearly correlated with the TIACs of 177Lu-DOTA-TATE in the IMR32-SSTR2 tumor, kidneys, brain, heart, liver, stomach and remainder body. The extrapolated %IA value at 0 hr of 68Ga-DOTA-TATE linearly correlated with the TIACs of 177Lu-DOTA-TATE in the IMR32 tumor and lungs. In our murine study, both kidneys and lungs were organs that showed high absorbed doses of 177Lu-DOTA-TATE.

Bivalves hold an important role in marine aquaculture and the identification of growth-related genes in bivalves could contribute to a better understanding of the mechanism governing their growth, which may benefit high-yielding bivalve breeding. Somatostatin receptor (SSTR) is a conserved negative regulator of growth in vertebrates. Although SSTR genes have been identified in invertebrates, their involvement in growth regulation remains unclear. Here, we identified seven SSTRs (PySSTRs) in the Yesso scallop, Patinopecten yessoensis, which is an economically important bivalve cultured in East Asia. Among the three PySSTRs (PySSTR-1, -2, and -3) expressed in adult tissues, PySSTR-1 showed significantly lower expression in fast-growing scallops than in slow-growing scallops. Then, the function of this gene in growth regulation was evaluated in dwarf surf clams (Mulinia lateralis), a potential model bivalve cultured in the lab, via RNA interference (RNAi) through feeding the clams Escherichia coli containing plasmids expressing double-stranded RNAs (dsRNAs) targeting MlSSTR-1. Suppressing the expression of MlSSTR-1, the homolog of PySSTR-1 in M. lateralis, resulted in a significant increase in shell length, shell width, shell height, soft tissue weight, and muscle weight by 20%, 22%, 20%, 79%, and 92%, respectively. A transcriptome analysis indicated that the up-regulated genes after MlSSTR-1 expression inhibition were significantly enriched in the fat digestion and absorption pathway and the insulin pathway. In summary, we systemically identified the SSTR genes in P. yessoensis and revealed the growth-inhibitory role of SSTR-1 in bivalves. This study indicates the conserved function of somatostatin signaling in growth regulation, and ingesting dsRNA-expressing bacteria is a useful way to verify gene function in bivalves. SSTR-1 is a candidate target for gene editing in bivalves to promote growth and could be used in the breeding of fast-growing bivalves. [ABSTRACT FROM AUTHOR]

In the present study, preparation of [188Re]Re-Tricine-HYNIC-Tyr3-octreotide, stability in human serum, internalization, cell viability analysis, and in vivo tissue biodistribution in rats bearing C6 glioma tumor were investigated. Radiolabeled peptide exhibited a molar activity of 8.60 ± 0.76 GBq/µmol, with over 90% (n = 3) of radiochemical yield. The findings indicated significant internalization of radiolabeled peptide into glioma cells and the ability to reduce cancerous cell viability in MTT analysis. High tumor-to-muscle ratios were observed at various time points following injection. The results suggest that the radiolabeled peptide could be considered for treating tumors expressing somatostatin receptors. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the relation between thyroid-stimulating-hormone (TSH) and metabolic tumor volume (MTV) in patients with advanced medullary thyroid cancer. Methods: Ga-68-DOTA-TATE-PET/CT findings such whole-body somatostatin receptor-expressing metabolic tumor volume (SSR-E MTV) and total lesion volume (SSR-E TLV) were calculated, and correlation analysis was performed for TSH and whole-body SSR-E MTV and SSR-E TLV. Results: Totally twenty-eight patients were included in the study. The median TSH level was 2.90 mU/L and median free T4 was 2.70 ng/L. The median calcitonin level was 6671.6 pg/mL and the median carcinoembryonic antigen level was 202.8 ng/mL. Median whole-body SSR-E MTV was calculated as 37.2 cm3 and median SSR-E TLV was calculated 198.6 cm3. There was a significantly positive correlation between TSH and whole-body SSR-E MTV and SSR-E TLV (rho=0.739, p<0.001 and rho=0.595, p=0.006). In the linear regression analysis, only calcitonin was found as a significant factor in terms of correlated with for SSR-E MTV (p<0.001). there were found that calcitonin and TSH were statistically significant factors in terms of correlated with SSR-E TLV (p<0.001 and p=0.005, respectively). Conclusion: This is the first study shown that a positive correlation between TSH and SSR-E MTV in patients with advanced medullary thyroid cancer. [ABSTRACT FROM AUTHOR]

Key Clinical Message: Radioligand Therapy (RLT) in the form of [177Lu] Lu‐DOTA‐TATE (Lutathera®) is a promising treatment for pancreatic neuroendocrine tumors (pNETs) with cardiac metastasis. We present a patient treated with [177Lu] Lu‐DOTA‐TATE that showed shrinkage of metastasis after four treatments at 7.4 GBq every 8 weeks. [ABSTRACT FROM AUTHOR]

Abstract Objectives The standard treatment for canine and feline meningiomas includes radiotherapy, surgical excision or combined therapy. However, new therapeutic approaches are required due to the possible recurrence or progression of meningiomas despite initial therapy. Adjunctive therapy with synthetic long‐acting somatostatin (SST) analogues has been described in humans with SST‐expressing tumours. The expression of SST receptors (SSTRs) by feline meningiomas is currently unknown, and there are little data about canine meningiomas. We hypothesized that SSTR is expressed by canine and feline meningiomas (S1). Methods Seven canines and 11 felines with histologically confirmed meningiomas underwent STTR screening. RNA expressions of SSTR1, SSTR2, SSTR3 and SSTR5 (canine) and SSTR1–SSTR 5 (feline) in fresh frozen and formalin‐fixed and paraffin‐embedded (FFPE) samples were investigated using real‐time (RT)‐qPCR. The expression of SSTR1 and SSTR2 in FFPE samples was evaluated using immunohistochemistry (IHC). The specificity of applied antibodies for canine and feline species was confirmed by western blotting. Results In canine meningiomas (n = 7), RNA expression of SSTR1, SSTR2 and SSTR5 was detected in all samples; SSTR3 RNA expression was detected in only 33% of samples. In feline meningiomas (n = 12), RNA expression of SSTR1, SSTR4, SSTR5 and SSTR2 was detected in 91%, 46%, 46% and 36% of samples, respectively; SSTR3 was not expressed. Overall, the detection rate was lower in FFPE samples. IHC revealed the expression of SSTR1 and SSTR2 in all samples from both species. However, it is important to exercise caution when interpreting IHC results due to the presence of diffuse background staining. Conclusions SSTRs are widely expressed in canine and feline meningiomas, thereby encouraging further studies investigating SSTR expression to conduct trials about the effect of adjunctive therapy with long‐acting SST‐analogues.

Background/Objectives: Myocarditis is an inflammatory disease of the myocardium and remains to this day a challenging diagnosis. A promising novel imaging method uses the expression of somatostatin receptors (SSTRs) on inflammatory cells to visualize myocardial inflammation. However, little is known about the histopathological correlate of SSTR imaging in different forms of myocarditis. Methods: In the present retrospective histopathological study, we systematically analysed the expression of SSTR subtype 2 (SSTR2) on inflammatory cells of 33 patients with biopsy- or explant-proven myocarditis (lymphocytic myocarditis (n = 5), giant-cell myocarditis (n = 11), and cardiac sarcoidosis (n = 17)), and in eight controls (multi-organ donors) without signs of myocardial inflammation and/or scars. Results: In all patients, immunohistochemical staining for SSTR2 was positive in areas with CD68-positive macrophages and multinucleated giant cells. Staining for SSTR2 was most prominent in the presence of multinucleated giant cells. The colocalization of both SSTR2 and CD68 on the same cell could be confirmed using immunofluorescence microscopy. Western blotting confirmed the upregulated expression of SSTR2 in cases of granulomatous inflammation (sarcoidosis) of the skeletal and heart muscle, in comparison with controls. Conclusions: In conclusion, our findings demonstrate the expression of SSTR2 on the protein level on CD68-positive macrophages and multinucleated giant cells in various forms of myocarditis, which provides a clear rationale for the diagnostic use of SSTR imaging in this patient group.

Introduction: Neuroendocrine neoplasms (NEN) are a rare and heterogenous group of tumors arising from neuroendocrine cells in multiple organs. Neuroendocrine tumors (NET) G3 encompass a small subgroup accounting for less than 10% of all neuroendocrine neoplasms. In contrast to NET G1 and G2 as well as neuroendocrine carcinomas (NEC), in NET G3 data on treatment and patient outcomes are still limited. Especially in a metastasized tumor stage, the role of surgery, peptide receptor radionucleotide therapy (PRRT), and systemic chemotherapy is not clearly defined. Methods: In this real-life cohort, we consecutively analyzed clinical outcome in NET G3 patients receiving different diagnostic and treatment. Results and discussion: We found that even metastasized NET G3 patients undergoing surgery, or receiving radiation, somatostatin analogues (SSA), and PRRT showed a clear survival benefit. Interestingly, all treatment regimen were superior to classical chemotherapeutic agents. In addition, somatostatin receptor (SSTR) PET-CT, FDG PET-CT, and repetitive biopsies were shown to be useful diagnostic and prognostic tools in NET G3. Our study demonstrates that patients with highly proliferative NET G3 might benefit from less aggressive treatment modalities commonly used in low proliferative NEN. [ABSTRACT FROM AUTHOR]

Purpose: Tumor resection represents the first-line treatment for symptomatic meningiomas, and the extent of resection has been shown to be of prognostic importance. Assessment of tumor remnants with somatostatin receptor PET proves to be superior to intraoperative estimation with Simpson grading or MRI. In this preliminary study, we evaluate the prognostic relevance of postoperative PET for progression-free survival in meningiomas. Methods: We conducted a post hoc analysis on a prospective patient cohort with resected meningioma WHO grade 1. Patients received postoperative MRI and [68Ga]Ga-DOTA-TATE PET/CT and were followed regularly with MRI surveillance scans for detection of tumor recurrence/progression. Results: We included 46 patients with 49 tumors. The mean age at diagnosis was 57.8 ± 1.7 years with a male-to-female ratio of 1:1.7. Local tumor progression occurred in 7/49 patients (14%) after a median follow-up of 52 months. Positive PET was associated with an increased risk for progression (*p = 0.015) and a lower progression-free survival (*p = 0.029), whereas MRI was not. 20 out of 20 patients (100%) with negative PET findings remained recurrence-free. The location of recurrence/progression on MRI was adjacent to regions where postoperative PET indicated tumor remnants in all cases. Gross tumor volumes were higher on PET compared to MRI (*p = 0.032). Conclusion: Our data show that [68Ga]Ga-DOTA-TATE PET/CT is highly sensitive in revealing tumor remnants in patients with meningioma WHO grade 1. Negative PET findings were associated with a higher progression-free survival, thus improving surveillance. In patients with tumor remnants, additional PET can optimize adjuvant radiotherapy target planning of surgically resected meningiomas. [ABSTRACT FROM AUTHOR]

Key Clinical Message Radioligand Therapy (RLT) in the form of [177Lu] Lu‐DOTA‐TATE (Lutathera®) is a promising treatment for pancreatic neuroendocrine tumors (pNETs) with cardiac metastasis. We present a patient treated with [177Lu] Lu‐DOTA‐TATE that showed shrinkage of metastasis after four treatments at 7.4 GBq every 8 weeks.

Objective: In this study, we aimed to investigate the physiological biodistribution pattern of 68Ga- DOTATATE and DOTANOC using standardized uptake value (SUV) parameters (maximum and mean) in nontumorous tissues on positron emission tomography/computed tomography (PET/CT) images. Methods: Images of 40 patients (female, n=23 and male, n=17; mean age, 52.50+-15.82 years) who had undergone 68Ga-DOTA labeled (TATE or NOC) PET/CT imaging with the diagnosis of GEPneuroendocrine tumor (NET), non-GEP-NET and thyroid cancer were retrospectively evaluated. SUVmax and SUVmean measurements were performed from areas of physiologic uptake including pituitary gland, parotid and submandibular gland, palatine tonsils, thyroid, lungs, blood pool, thymus, lymph nodes, liver, pancreas (from head, body and tail parts), spleen, stomach, both adrenal gland, kidney, small bowel and colon, bone marrow, prostate, glandular breast tissue and muscle tissue. Results: The highest uptake for 68Ga-DOTATATE and 68Ga-DOTATANOC was noted in the spleen, adrenal, kidney, liver, pituitary gland and head of the pancreas, respectively. Lung, muscle, blood pool, bone marrow, lymph node and breast showed low uptake (SUVmax-mean

Abstract Background Fluorine-18-labeled SSAs have the potential to become the next-generation tracer in SSTR-imaging in neuroendocrine tumor (NET) patients given their logistical advantages over the current gold standard gallium-68-labeled SSAs. In particular, [18F]AlF-OC has already shown excellent clinical performance. We demonstrated in our previous report from our prospective multicenter trial that [18F]AlF-OC PET/CT outperforms [68Ga]Ga-DOTA-SSA, but histological confirmation was lacking due to ethical and practical reasons. In this second arm, we therefore aimed to provide evidence that the vast majority of [18F]AlF-OC PET lesions are in fact true NET lesions by analyzing their MR characteristics on simultaneously acquired MRI. We had a special interest in lesions solely detected by [18F]AlF-OC (“incremental lesions”). Methods Ten patients with a histologically confirmed neuroendocrine tumor (NET) and a standard-of-care [68Ga]Ga-DOTATATE PET/CT, performed within 3 months, were prospectively included. Patients underwent a whole-body PET/MRI (TOF, 3 T, GE Signa), 2 hours after IV injection of 4 MBq/kg [18F]AlF-OC. Positive PET lesions were evaluated for a corresponding lesion on MRI. The diagnostic performance of both PET tracers was evaluated by determining the detection ratio (DR) for each scan and the differential detection ratio (DDR) per patient. Results In total, 195 unique lesions were detected: 167 with [68Ga]Ga-DOTATATE and 193 with [18F]AlF-OC. The DR for [18F]AlF-OC was 99.1% versus 91.4% for [68Ga]Ga-DOTATATE, significant for non-inferiority testing (p = 0.0001). Out of these 193 [18F]AlF-OC lesions, 96.2% were confirmed by MRI to be NET lesions. Thirty-three incremental lesions were identified by [18F]AlF-OC, of which 91% were confirmed by MRI and considered true positives. Conclusion The DR of [18F]AlF-OC was numerically higher and non-inferior to the DR of [68Ga]Ga-DOTATATE. [18F]AlF-OC lesions and especially incremental lesions were confirmed as true positives by MRI in more than 90% of lesions. Taken together, these data further validate [18F]AlF-OC as a new alternative for SSTR PET in clinical practice. Trial registration ClinicalTrials.gov: NCT04552847. Registered 17 September 2020, https://beta.clinicaltrials.gov/study/NCT04552847

Tumor-specific overexpression of receptors enables a variety of targeted cancer therapies, exemplified by peptide-receptor radiotherapy (PRRT) for somatostatin receptor (SSTR)-positive neuroendocrine tumors. While effective, PRRT is restricted to tumors with SSTR overexpression. To overcome this limitation, we propose using oncolytic vaccinia virus (vvDD)-mediated receptor gene transfer to permit molecular imaging and PRRT in tumors without endogenous SSTR overexpression, a strategy termed radiovirotherapy. We hypothesized that vvDD-SSTR combined with a radiolabeled somatostatin analog could be deployed as radiovirotherapy in a colorectal cancer peritoneal carcinomatosis model, producing tumor-specific radiopeptide accumulation. Following vvDD-SSTR and 177Lu-DOTATOC treatment, viral replication and cytotoxicity, as well as biodistribution, tumor uptake, and survival, were evaluated. Radiovirotherapy did not alter virus replication or biodistribution, but synergistically improved vvDD-SSTR-induced cell killing in a receptor-dependent manner and significantly increased the tumor-specific accumulation and tumor-to-blood ratio of 177Lu-DOTATOC, making tumors imageable by microSPECT/CT and causing no significant toxicity. 177Lu-DOTATOC significantly improved survival over virus alone when combined with vvDD-SSTR but not control virus. We have therefore demonstrated that vvDD-SSTR can convert receptor-negative tumors into receptor-positive tumors and facilitate molecular imaging and PRRT using radiolabeled somatostatin analogs. Radiovirotherapy represents a promising treatment strategy with potential applications in a wide range of cancers.

IntroductionNeuroendocrine neoplasms (NEN) are a rare and heterogenous group of tumors arising from neuroendocrine cells in multiple organs. Neuroendocrine tumors (NET) G3 encompass a small subgroup accounting for less than 10% of all neuroendocrine neoplasms. In contrast to NET G1 and G2 as well as neuroendocrine carcinomas (NEC), in NET G3 data on treatment and patient outcomes are still limited. Especially in a metastasized tumor stage, the role of surgery, peptide receptor radionucleotide therapy (PRRT), and systemic chemotherapy is not clearly defined.MethodsIn this real-life cohort, we consecutively analyzed clinical outcome in NET G3 patients receiving different diagnostic and treatment.Results and discussionWe found that even metastasized NET G3 patients undergoing surgery, or receiving radiation, somatostatin analogues (SSA), and PRRT showed a clear survival benefit. Interestingly, all treatment regimen were superior to classical chemotherapeutic agents. In addition, somatostatin receptor (SSTR) PET-CT, FDG PET-CT, and repetitive biopsies were shown to be useful diagnostic and prognostic tools in NET G3. Our study demonstrates that patients with highly proliferative NET G3 might benefit from less aggressive treatment modalities commonly used in low proliferative NEN.

Simple Summary: Radioligand therapy with [177Lu]Lu-DOTA-TATE is a therapeutic option for adult patients with somatostatin-receptor–positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Patients undergoing radioligand therapy require diligent monitoring and surveillance. While published guidelines can provide guidance on general approaches to care, GEP-NETs are heterogeneous and the guidelines can be difficult to apply in individual and complex cases. In this article, we discuss emerging evidence on imaging, clinical biochemistry, and tumor assessment criteria in the management of patients receiving radioligand therapy for GEP-NETs as well as our own best practices. We offer practical guidance on how to effectively implement monitoring and surveillance measures to aid patient-tailored clinical decision-making. Radioligand therapy (RLT) with [177Lu]Lu-DOTA-TATE is a standard of care for adult patients with somatostatin-receptor (SSTR)-positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Taking advantage of this precision nuclear medicine approach requires diligent monitoring and surveillance, from the use of diagnostic SSTR-targeted radioligand imaging for the selection of patients through treatment and assessments of response. Published evidence-based guidelines assist the multidisciplinary healthcare team by providing acceptable approaches to care; however, the sheer heterogeneity of GEP-NETs can make these frameworks difficult to apply in individual clinical circumstances. There are also contradictions in the literature regarding the utility of novel approaches in monitoring and surveilling patients with GEP-NETs receiving RLT. This article discusses the emerging evidence on imaging, clinical biochemistry, and tumor assessment criteria in the management of patients receiving RLT for GEP-NETs; additionally, it documents our own best practices. This allows us to offer practical guidance on how to effectively implement monitoring and surveillance measures to aid patient-tailored clinical decision-making. [ABSTRACT FROM AUTHOR]

Prolactin (PRL) and growth hormone (GH) are peptide hormones that bind to the class 1 cytokine receptor superfamily, a highly conserved cell surface class of receptors. Both hormones control their own secretion via a negative autocrine loop in their own mammosomatotroph, lactotroph or somatotroph. In this regard, GH and PRL are regulated by similar signaling pathways involving cell growth and hormone secretion. Thus, GH and PRL dysregulation and pituitary neuroendocrine tumor (PitNET) development may have common pathogenic pathways. Based on cell linage, lactotroph and somatotroph PitNETs come from pituitary-specific POU-class homeodomain transcription factor (Pit-1). Mammosomatotroph and plurihormonal PitNETs are a unique subtype of PitNETs that arise from a single-cell population of Pit-1 lineage. In contrast, mixed somatotroph–lactotroph PitNETs are composed of two distinct cell populations: somatotrophs and lactotrophs. Morphologic features that distinguish indolent PitNETs from locally aggressive ones are still unidentified, and no single prognostic parameter can predict tumor aggressiveness or treatment response. In this review, we aim to explore the latest research on lactotroph and somatotroph PitNETs, the molecular mechanisms involved in PRL and GH axis regulation and the signaling pathways involved in their aggressiveness, particularly focused on mammosomatotroph and mixed subtypes. Finally, we summarize epidemiological, clinical, and radiological features of these exceptional tumors. We aim to shed light, from basic to clinical settings, on new perspectives and scientific gaps in this field. [ABSTRACT FROM AUTHOR]

Merkel cell carcinoma (MCC) is a rare, high-grade neuroendocrine neoplasm (NEN) of the skin. Somatostatin receptors (SSTRs) are G protein-linked receptors that regulate cell proliferation and growth. SSTRs are expressed in many NENs; however, scant information is available on their expression in MCCs or their association with clinical parameters and patient outcomes. This retrospective study was conducted at Helsinki University Hospital and the University of Helsinki. Using a tissue microarray, we investigated SSTR1-5 expression by immunohistochemistry in 99 MCC tissue samples. Samples were collected between 1983 and 2017 and coupled with the patients' clinical data. SSTR2-SSTR5 were detected in 69%, 6%, 4%, and 1% of the tumours, respectively. However, SSTR1 expression was not observed. Cytoplasmic SSTR2 positivity was associated with metastatic disease at the time of diagnosis (p = 0.009), but it did not correlate with disease-specificity or overall survival. SSTR2-5 expression was observed in MCCs. In particular, SSTR2 expression is clinically valid because it is associated with metastatic disease at the time of diagnosis and can thus serve as a prognostic marker. Moreover, SSTR2 overexpression provides a molecular basis for tumour imaging and treatment with somatostatin analogues. [ABSTRACT FROM AUTHOR]

Somatostatin receptor (SSTR)-targeted peptide receptor radionuclide therapy (PRRT) represents a promising approach for treatment-refractory meningiomas. Methods: We performed an individual patient data meta-analysis, including all published data on meningioma patients treated with SSTR-targeted PRRT. The main outcomes were toxicity, response to treatment, progression-free survival (PFS), and overall survival (OS). We applied the Kaplan-Meier method to estimate survival probabilities and report incidence rates per 100 person-years. We applied Cox proportional hazards models to determine the effect of covariates. Results: We screened 537 papers and identified 6 eligible cohort studies. We included a total of 111 patients who had treatment-refractory meningioma and received SSTR-targeted PRRT. Disease control was achieved in 63% of patients. The 6-mo PFS rates were 94%, 48%, and 0% for World Health Organization grades I, II, and III, respectively. The risk of disease progression decreased by 13% per 1,000-MBq increase in the total applied activity. The 1-y OS rates were 88%, 71%, and 52% for World Health Organization grades I, II, and III, respectively. The risk of death decreased by 17% per 1,000-MBq increase in the total applied activity. The main side effects comprised transient hematotoxicity, such as anemia in 22% of patients, leukopenia in 13%, lymphocytopenia in 24%, and thrombocytopenia in 17%. Conclusion: To our knowledge, this individual patient data meta-analysis represents the most comprehensive analysis of the benefits of and adverse events associated with SSTR-targeted PRRT for treatment-refractory meningioma. The treatment was well tolerated, achieved disease control in most cases, and showed promising results regarding PFS and OS.

Abstract Background The accumulation of 177Lu-DOTATATE might be influenced by the amount of administered peptide in relation to the tumor somatostatin receptor expression. The effect of the administered peptide mass on the resulting absorbed dose in tumors and normal organs has not previously been assessed in relation to the patients’ tumor load. Method Patients with small intestinal (n = 141) and pancreatic (n = 62) neuroendocrine tumors (NETs) who underwent PRRT were selected for retrospective evaluation. All patients had received 7.4 GBq 177Lu-DOTATATE, and the amount of administered peptide in the preparation varied from 93 to 456 µg. The absorbed dose in tumors and normal tissue at the first PRRT cycle was calculated, based on SPECT-measurements at day 1, 4, and 7 post-infusion. The total tumor somatostatin receptor expression (tTSSTRE) was calculated on SPECT after 24 h by multiplying the functional tumor volume, delineated by 42% cut-off VOIs of the highest activity, with the SUVmean for the respective tumor VOIs. Spearman’s rank correlation analyzed any relationship between the administered amount of peptide and the absorbed dose in tumors and normal organs, in relation to the patients’ tTSSTRE. Results There was no correlation between the amount of peptide and any of the tested parameters in relation to tTSSTRE. Conclusion In this retrospective analysis, no correlation between the amount of administered peptide in the 177Lu-DOTATATE preparation and the absorbed radiation doses in tumors and normal tissues was demonstrated in relation to the total tumor SSTR expression.

Neuroendocrine tumors(NETs) are a group of heterogeneous tumors originating from neuroendocrine cells. They can occur anywhere in the body, most commonly in the digestive tract, pancreas, and lungs. The incidence and prevalence of NET have been increasing in recent years. Early diagnosis of NET has been difficult. Somatostatin receptor(SSTR), as the most common peptide hormone receptor in NET, has become an important target in NET drug development. Radionuclide-labeled somatostatin analogs can specifically bind to SSTR over-expressed on the surface of NET cells. Therefore, such radiopharmaceuticals can be used for early diagnosis and targeted therapy of NET. So far, several SSTR-targeted radiopharmaceuticals have been approved for marketing by the U.S. Food and Drug Administration(FDA), European Medicines Agency(EMA) and other agencies, but no such radiopharmaceuticals have been marketed in China. This review first introduces the relationship between neuroendocrine tumors and SSTR, and the development history of SSTR-targeted metal-based radiopharmaceuticals, and summarizes the diagnostic and therapeutic radiopharmaceuticals that have been approved by the FDA and other drug regulatory authorities in various countries. The different characteristics of SSTR antagonists and antagonist drugs are discussed, and the related research progress of SSTR antagonists in the field of radioactive diagnosis and therapy is remarked. Metal-based radiopharmaceuticals targeting SSTR antagonists have initially shown better diagnostic and therapeutic effects than agonists, and may have good application prospects.

Somatostatin receptor scintigraphy is a key diagnostic tool in the initial staging and therapeutic evaluation of neuroendocrine tumors. Its specificity can be compromised by the presence of false positives. We illustrate here the case of a vertebral hemangioma detected on 99mTc-Tektrotyd scintigraphy as an incidental finding in a 34-year-old man referred for the staging of a well-differentiated neuroendocrine tumor of the ampulla of Vater (Fig. 1). [ABSTRACT FROM AUTHOR]

Objectives: Tumor-induced osteomalacia (TIO) is a rare acquired paraneoplastic disorder characterized by hypophosphatemia resulting from tumor-secreted fibroblast growth factor-23 (FGF23). Surgical resection of the culprit TIO is the first choice of treatment. However, TIO is difficult to detect with conventional diagnostic tools due to its small size and variable location in the body. Somatostatin receptor scintigraphy (SSR) has recently emerged as a functional molecular imaging choice for TIO detection and localization. This research was undertaken to evaluate the efficacy of 99mTc-labeled hydrazinonicotinyl-Tyr3-octreotide (99mTc-HYNIC-TOC) SPECT/CT in detecting TIO. Methods: 99mTc-HYNIC-TOC SPECT/CT and the available clinical data of 25 patients with suspected TIO were analyzed retrospectively. The 99mTc-HYNICTOC SPECT/CT findings were compared with the post-surgical pathology diagnosis and clinical follow-up results. Results: Using 99mTc-HYNIC-TOCSPECT/CT, suspicious tumorswere found in 18 of the 25 patients, and 15 of them underwent surgical resection. The postoperative pathology confirmed a TIO in those 13 patients whose symptoms and biochemical anomalies gradually resolved after the surgery. The remaining five patients were finally considered false positives. Moreover, the 99mTc-HYNIC-TOC SPECT/CT results were negative in seven patients, with six patients being true negative (4 patients were diagnosed with acquired Fanconi syndrome and 2 patients responded well to conservative therapy) and one being false negative. Therefore, the sensitivity and specificity values of 99mTc-HYNIC-TOC SPECT/CT in the evaluation of TIO were 92.9% (13/14) and 54.5% (6/11), respectively. The overall accuracy of 99mTc-HYNIC-TOC SPECT/CT for detecting TIO was 76.0% (19/25). Conclusions: The 99mTc-HYNIC-TOC SPECT/CT is an accurate imaging modality for locating culprit tumors in TIO. [ABSTRACT FROM AUTHOR]

Simple Summary: Currently, the diagnosis of salivary gland tumors using current imaging techniques is unreliable. In this study we examined salivary gland tumors and discovered that the pleomorphic adenoma, a tumor which should be surgically removed because it has a tendency to become malign, has a strong concentration of the somatostatin receptor 2. This characteristic may allow physicians to identify and potentially treat the tumor in a non-invasive manner. Reliable preoperative diagnosis between salivary gland tumor entities is difficult. In this monocentric retrospective study, we examined the somatostatin receptor 2 (SSTR2) status of salivary gland tumors after salivary gland tumor resection via immunohistochemistry (IHC), and stains were compared in analogy to the HER2 mamma scale. A total of 42.3% of all pleomorphic adenoma (PA) tumors (42 of 99, 95% confidence interval 32.5–52.8%) demonstrated ≥20% of cells displaying the SSTR2 as compared to just 1% of all other tumors (1/160, 95% CI 0.02–3.4%). The other tumor was a neuroendocrine carcinoma. PA had a higher intensity of SSTR2 staining, with 90.9% staining ≥ an intensity of 2 (moderate). Tumors with an intensity of SSTR2 expression equal to or greater than 2 had an 89.9% likelihood of being a PA (95% CI: 82.2–95.0%, AUC: 0.928). Only one Warthin tumor demonstrated a 'strong' SSTR2 staining intensity. No Warthin tumor showed a percentage of cells staining for SSTR2 above ≥20%. This result demonstrates consistent and strong expression of SSTR2 in PAs as compared to Warthin tumors, which may allow physicians to utilize radioligand-somatostatin analog PET CT/MR imaging to diagnose the PA. SSTR2 positivity, if shown to be clinically relevant, may allow peptide receptor radionuclide therapy in the future. [ABSTRACT FROM AUTHOR]

Key Clinical Message: Octreotide is used in patients with insulinomas to treat hypoglycemia, and somatostatin receptor (SSTR) 2 expression is important for its efficacy. We report a case of insulinoma in a 50‐year‐old woman that responded to an octreotide test, showed accumulation in somatostatin scintigraphy, and was positive for SSTR2A on immunostaining. [ABSTRACT FROM AUTHOR]

As a new medical technology, the integration of diagnosis and treatment has broad application prospects. Among them, the integration of diagnosis and treatment of nuclear medicine is a hot spot in today's research and an important direction for the future development of nuclear medicine. It combines radionuclide imaging with radionuclide internal irradiation therapy, which can create conditions for realizing personalized diagnosis and treatment of tumors. At present, a variety of integrated drugs for radionuclide diagnosis and treatment have been developed for different targets, and some drugs have been successfully applied in clinic, especially in prostate cancer, neuroendocrine tumors and other fields. Molecular probe-based targeted imaging and targeted therapy drugs based on radionuclides bring new hope for the diagnosis and treatment of some refractory tumors. It is particularly important to independently develop different types of integrated drugs for diagnosis and treatment and push them into preclinical and clinical trial research, so as to better serve the clinical individualized diagnosis and treatment. [ABSTRACT FROM AUTHOR]

Simple Summary: Despite novel targeted treatment options, small cell lung cancer (SCLC) still has a bad prognosis. However, as a relevant number of SCLC patients show a high expression of somatostatin receptors (SSTRs), SSTR-targeted radionuclide therapy (PRRT) may be a treatment option. Therefore, we investigated whether SSTR expression assessed in positron emission tomography (PET) has prognostic value. In patients with adequate PET uptake, PRRT was performed, and the outcome was investigated. We found that SSTR-targeted PET, although not a prognostic tool for outcome, is an important tool for treatment decision. In some patients, PRRT can be a promising treatment option as a second or third line treatment of SCLC. Background: Given the dismal prognosis of small cell lung cancer (SCLC), novel therapeutic targets are urgently needed. We aimed to evaluate whether SSTR expression, as assessed by positron emission tomography (PET), can be applied as a prognostic image biomarker and determined subjects eligible for peptide receptor radionuclide therapy (PRRT). Methods: A total of 67 patients (26 females; age, 41–80 years) with advanced SCLC underwent SSTR-directed PET/computed tomography (somatostatin receptor imaging, SRI). SRI-avid tumor burden was quantified by maximum standardized uptake values (SUVmax) and tumor-to-liver ratios (T/L) of the most intense SCLC lesion. Scan findings were correlated with progression-free (PFS) and overall survival (OS). In addition, subjects eligible for SSTR-directed radioligand therapy were identified, and treatment outcome and toxicity profile were recorded. Results: On a patient basis, 36/67 (53.7%) subjects presented with mainly SSTR-positive SCLC lesions (>50% lesions positive); in 10/67 patients (14.9%), all lesions were positive. The median SUVmax was found to be 8.5, while the median T/L was 1.12. SRI-uptake was not associated with PFS or OS, respectively (SUVmax vs. PFS, ρ = 0.13 with p = 0.30 and vs. OS, ρ = 0.00 with p = 0.97; T/L vs. PFS, ρ = 0.07 with p = 0.58 and vs. OS, ρ = −0.05 with p = 0.70). PRRT was performed in 14 patients. One patient succumbed to treatment-independent infectious complications immediately after PRRT. In the remaining 13 subjects, disease control was achieved in 5/13 (38.5%) with a single patient achieving a partial response (stable disease in the remainder). In the sub-group of responding patients, PFS and OS were 357 days and 480 days, respectively. Conclusions: SSTR expression as detected by SRI is not predictive of outcome in patients with advanced SCLC. However, it might serve as a therapeutic target in selected patients. [ABSTRACT FROM AUTHOR]

Simple Summary: The monitoring of disease in patients with neuroendocrine tumors is challenging and requires specialized imaging techniques. To address these quests, somatostatin receptor-targeting molecular imaging modalities that can accurately visualize disease manifestations of neuroendocrine tumors have been proposed. However, the prognostic value of the total tumor volume, expression level, and related metrics has yet to be thouroughly understood. Historically, molecular imaging of somatostatin receptor (SSTR) expression in patients with neuroendocrine tumors (NET) was performed using SSTR scintigraphy (SRS). Sustained advances in medical imaging have led to its gradual replacement with SSTR positron-emission tomography (SSTR-PET). The higher sensitivity in comparison to SRS on the one hand and conventional cross-sectional imaging, on the other hand, enables more accurate staging and allows for image quantification. In addition, in recent years, a growing body of evidence has assessed the prognostic implications of SSTR-PET-derived prognostic biomarkers for NET patients, with the aim of risk stratification, outcome prognostication, and prediction of response to peptide receptor radionuclide therapy. In this narrative review, we give an overview of studies examining the prognostic value of advanced SSTR-PET-derived (semi-)quantitative metrics like tumor volume, uptake, and composite metrics. Complementing this analysis, a discussion of the current trends, clinical implications, and future directions is provided. [ABSTRACT FROM AUTHOR]

Somatostatin receptor (SSTR) agonist-based Positron Emission Tomography-Computed Tomography (PET-CT) imaging is nowadays the mainstay for the assessment and diagnostic imaging of neuroendocrine neoplasms (NEN), especially in well-differentiated neuroendocrine tumors (NET) (World Health Organization (WHO) grade I and II). Major clinical indications for SSTR imaging are primary staging and metastatic workup, especially (a) before surgery, (b) detection of unknown primary in metastatic NET, (c) patient selection for theranostics and appropriate therapy, especially peptide receptor radionuclide therapy (PRRT), while less major indications include treatment response evaluation on and disease prognostication. Dual tracer PET-CT imaging using SSTR targeted PET tracers, viz. [68Ga]Ga-DOTA-Tyr3-Octreotate (DOTA-TATE) and [68Ga]Ga-DOTA-NaI3-Octreotide (DOTA-NOC), and fluorodeoxyglucose (FDG), have recently gained widespread acceptance for better assessment of whole-body tumor biology compared to single-site histopathology, in terms of being non-invasive and the ability to assess inter- and intra-tumoral heterogeneity on a global scale. FDG uptake has been identified as independent adverse risk factor in various studies. Recently, somatostatin receptor antagonists have been shown to be more sensitive and specific in detecting the disease. The aim of this review article is to summarize the clinical importance of SSTR-based imaging in the clinical management of neuroendocrine and related tumors. [ABSTRACT FROM AUTHOR]

Copyright of Acta Facultatis Medicae Naissensis is the property of Nis University, Faculty of Medicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Fluorine-18-labeled SSAs have the potential to become the next-generation tracer in SSTR-imaging in neuroendocrine tumor (NET) patients given their logistical advantages over the current gold standard gallium-68-labeled SSAs. In particular, [18F]AlF-OC has already shown excellent clinical performance. We demonstrated in our previous report from our prospective multicenter trial that [18F]AlF-OC PET/CT outperforms [68Ga]Ga-DOTA-SSA, but histological confirmation was lacking due to ethical and practical reasons. In this second arm, we therefore aimed to provide evidence that the vast majority of [18F]AlF-OC PET lesions are in fact true NET lesions by analyzing their MR characteristics on simultaneously acquired MRI. We had a special interest in lesions solely detected by [18F]AlF-OC ("incremental lesions"). Methods: Ten patients with a histologically confirmed neuroendocrine tumor (NET) and a standard-of-care [68Ga]Ga-DOTATATE PET/CT, performed within 3 months, were prospectively included. Patients underwent a whole-body PET/MRI (TOF, 3 T, GE Signa), 2 hours after IV injection of 4 MBq/kg [18F]AlF-OC. Positive PET lesions were evaluated for a corresponding lesion on MRI. The diagnostic performance of both PET tracers was evaluated by determining the detection ratio (DR) for each scan and the differential detection ratio (DDR) per patient. Results: In total, 195 unique lesions were detected: 167 with [68Ga]Ga-DOTATATE and 193 with [18F]AlF-OC. The DR for [18F]AlF-OC was 99.1% versus 91.4% for [68Ga]Ga-DOTATATE, significant for non-inferiority testing (p = 0.0001). Out of these 193 [18F]AlF-OC lesions, 96.2% were confirmed by MRI to be NET lesions. Thirty-three incremental lesions were identified by [18F]AlF-OC, of which 91% were confirmed by MRI and considered true positives. Conclusion: The DR of [18F]AlF-OC was numerically higher and non-inferior to the DR of [68Ga]Ga-DOTATATE. [18F]AlF-OC lesions and especially incremental lesions were confirmed as true positives by MRI in more than 90% of lesions. Taken together, these data further validate [18F]AlF-OC as a new alternative for SSTR PET in clinical practice. Trial registration ClinicalTrials.gov: NCT04552847. Registered 17 September 2020, https://beta.clinicaltrials.gov/study/NCT04552847 [ABSTRACT FROM AUTHOR]

Simple Summary: This article discusses the use of peptide receptor radionuclide therapy (PRRT) as a key treatment method for advanced, unresectable neuroendocrine tumors. It covers the multidisciplinary theranostic approach, treatment effectiveness, patient outcomes, and toxicity of PRRT for neuroendocrine neoplasms. We will also examine important research, and explore new radiopharmaceuticals for the treatment of these patients. Neuroendocrine neoplasms (NENs) are tumors originating from neuroendocrine cells distributed throughout the human body. With an increasing incidence over the past few decades, they represent a highly heterogeneous group of neoplasms, mostly expressing somatostatin receptors (SSTRs) on their cell surface. Peptide receptor radionuclide therapy (PRRT) has emerged as a crucial strategy for treating advanced, unresectable neuroendocrine tumors by administering radiolabeled somatostatin analogs intravenously to target SSTRs. This article will focus on the multidisciplinary theranostic approach, treatment effectiveness (such as response rates and symptom relief), patient outcomes, and toxicity profile of PRRT for NEN patients. We will review the most significant studies, such as the phase III NETTER-1 trial, and discuss promising new radiopharmaceuticals, including alpha-emitting radionuclide-labeled somatostatin analogs and SSTR antagonists. [ABSTRACT FROM AUTHOR]