SDH-related head and neck paragangliomas: Unraveling PET radiomics beyond 18F-FDG.

Radiomics revolutionizes medical imaging by providing quantitative analysis that complements traditional qualitative assessments through advanced computational techniques. In this narrative review we have investigated the impact of succinate dehydrogenase (SDH) pathogenic variants on the radiomic profile of 18F-FDG, 18F-DOPA, and 68Ga-DOTA-peptides PET in paragangliomas, focusing on head and neck localizations (HNPGLs). This influence manifests in uptake intensity and textural heterogeneity, revealing a complex radiomic landscape that may reflect specific tumor behaviors and mutation statuses. By combining radiomic analysis with genetic data, we will gain new insights into the relationship between PET imaging features and underlying molecular changes. In the future, we envision an approach integrating macroscopic indices, such as lesion location, size, and SUV, with advanced computer-based algorithms. This comprehensive analysis could facilitate in vivo predictions of SDH pathogenic variants, thereby encouraging genetic testing, and ultimately improving patient outcomes.

68Ga-DOATATOC Brain PET/CT Imaging in a case of Dural Metastasis from Synovial Sarcoma.

We present the case of a 70-year-old male patient who underwent a gallium-68 (68Ga)-DOTATOC brain positron emission tomography (PET)/computed tomography (CT) for the assessment of a tumorous lesion on the dura. The patient had previously undergone below-knee amputation due to a mass of synovial sarcoma on the left foot and completed adjuvant chemotherapy approximately 3 months ago. Subsequently, a well-demarcated papillary solid mass located on the dura was surgically excised. Pathological examination confirmed that the dural metastasis originated from synovial sarcoma and post-operative magnetic resonance imaging (MRI) revealed no residual tumor. We conducted a 68Ga-DOTATOC brain PET/CT suspecting a meningioma given the presence of a dural mass. The result showed lower uptake (maximum standardized uptake [SUVmax 4.9]) than the pituitary gland (SUVmax 9.3). Thus, we successfully conducted a differential diagnosis of metastasis from the preexisting malignancy rather than the meningioma. 68Ga-DOTATOC PET/CT is a valuable tool for the differential diagnosis of meningioma. However, metastasis should also be considered, especially in patients with a history of malignancy and lesions showing mild 68Ga-DOTATOC uptake.

[68Ga]DOTATOC PET-derived radiomics to predict genetic background of head and neck paragangliomas: a pilot investigation.

PURPOSE: To investigate the [68Ga]DOTATOC PET radiomic profile of head and neck paragangliomas (HNPGLs) and identify radiomic characteristics useful as predictors of succinate dehydrogenase genes (SDHx) pathogenic variants. METHODS: Sporadic and SDHx HNPGL patients, who underwent [68Ga]DOTATOC PET/CT, were retrospectively included. HNPGLs were analyzed using LIFEx software, and extracted features were harmonized to correct for batch effects and confronted testing for multiple comparison. Stepwise discriminant analysis was conducted to remove redundancy and identify best discriminating features. ROC analysis was used to define optimal cut-offs. Multivariate decision-tree analysis was performed using CHAID method. RESULTS: 34 patients harboring 60 HNPGLs (51 SDHx in 25 patients) were included. Three sporadic and nine SDHx HNPGLs were metastatic. At stepwise discriminant analysis, both GLSZM-Zone Size Non-Uniformity (ZSNU, reflecting tumor heterogeneity) and IB-TLSRE (total lesion somatostatin receptor expression) were independent predictors of genetic status, with 96.4% of lesions and 91.6% of patients correctly classified after cross validation (p < 0.001). Among non-metastatic patients, GLSZM-ZSNU and IB-TLSRE were significantly higher in sporadic than SDHx HNPGLs (p < 0.001). No differences were revealed in metastatic patients. Decision-tree analysis highlights multifocality and IB-TLSRE as useful variables, correctly identifying 6/9 sporadic and 24/25 SDHx patients. Model failed to classify one SDHA and three sporadic patients (2 metastatic). CONCLUSION: Radiomics features GLSZM-ZSNU and IB-TLSRE appear to reflect HNPGLs SDHx status and tumor behavior (metastatic vs. non-metastatic). If validated, especially IB-TLSRE might represent a simple and time-efficient radiomic index for SDHx variants early screening and prediction of tumor behavior in HNPGL cases.

Prevalence of metastases outside the liver and abdominal lymph nodes on 68Ga-DOTATOC-PET/CT in patients with small intestinal and pancreatic neuroendocrine tumours.

Metastases outside the liver and abdominal/retroperitoneal lymph nodes are nowadays detected frequently in patients with neuroendocrine tumours (NETs), owing to the high sensitivity of positron emission tomography (PET) with Gallium-68-DOTA-somatostatin analogues (68Ga-SSA) and concomitant diagnostic computed tomography (CT). Our aim was to determine the prevalence of extra-abdominal metastases on 68Ga-DOTATOC-PET/CT in a cohort of patients with small intestinal (Si-NET) and pancreatic NET (Pan-NET), as well as that of pancreatic metastasis in patients with Si-NET. Among 2090 patients examined by 68Ga-DOTATOC-PET/CT at two tertiary referral centres, a total of 1177 patients with a history of Si- or Pan-NET, were identified. The most recent 68Ga-DOTATOC-PET/CT report for each patient was reviewed, and the location and number of metastases of interest were recorded. Lesions outside the liver and abdominal nodes were found in 26% of patients (n = 310/1177), of whom 21.5% (255/1177) were diagnosed with Si-NET and 4.5% (55/1177) Pan-NET. Bone metastases were found in 18.4% (215/1177), metastases to Virchow's lymph node in 7.1% (83/1177), and lung/pleura in 4.8% (56/1177). In the subset of 255 Si-NET patients, 5.4% (41/255) manifested lesions in the pancreas, 1.5% in the breast (18/255), 1.3% in the heart (15/255) and 1% in the orbita (12/255). In Si-NET patients, the Ki-67 proliferation index was higher in those with ≥2 metastatic sites of interest, than with 1 metastatic site, (p <0.001). Overall, extra-abdominal or pancreatic metastases were more often found in patients with Si-NET (34%) than in those with Pan-NET (13%) (p <0.001). Bone metastases were 2.6 times more frequent in patients with Si-NET compared to Pan-NET patients (p <0.001). Lesions to the breast and orbita were encountered in almost only Si-NET patients. In conclusion, lesions outside the liver and abdominal nodes were detected in as many as 26% of the patients, with different prevalence and metastatic patterns in patients with Si-NET compared to Pan-NET. The impact of such metastases on overall survival and clinical decision-making needs further evaluation.

Altered biodistribution of [68Ga]Ga-DOTA-TOC during somatostatin analogue treatment.

PURPOSE: The need for an interval between the administration of long-acting Somatostatin Receptor Analogues (SSA) and the [68Ga]Ga-DOTA-TATE PET has been questioned based on recent literature in the new EANM guidelines. Here an earlier studies showed that SSA injection immediately before SSTR PET had minimal effect on normal organ and tumor uptake (1). However, data are scarce and there are (small) differences between [68Ga]Ga-DOTA-TATE and [68Ga]Ga-DOTA-TOC binding affinity, and it remains unknown whether these findings can be directly translated to scans with [68Ga]Ga-DOTA-TOC as well. The purpose of this study was to assess the effect of SSA use on the biodistribution in a subsequent [68Ga]Ga-DOTA-TOC PET/CT and compare this intra-individually across several cycles of SSA treatments. METHODS: Retrospectively, 35 patients with NENs were included. [68Ga]Ga-DOTA-TOC PET at staging and after the 1st and 2nd cycle of SSA were included. SUVmean and SUVmax of blood, visceral organs, primary tumor and two metastases were determined. Also, the interval between SSA therapy and the PET scan was registered. RESULTS: Treatment with SSA resulted in a significantly higher bloodpool activity and lower visceral tracer uptake. This effect was maintained after a 2nd cycle of SSA therapy. Furthermore, there was an inverse relationship between bloodpool tracer availability and visceral tracer binding and a positive correlation between bloodpool tracer availability and primary tumor tracer uptake. With an interval of up to 5 days, there was a significantly higher bloodpool activity than at longer intervals. CONCLUSION: Absolute comparison of the SUV on [68Ga]Ga-DOTA-TOC PET should be done with caution as the altered biodistribution of the tracer after SSA treatment should be taken into account. We recommend not to perform a scan within the first 5 days after the injection of lanreotide.

Cervical Ganglioneuroblastoma Diagnosed by 68Ga-DOTATOC PET/CT in a Child with Opsoclonus Myoclonus Syndrome.

We performed a 68Ga-DOTATOC PET/CT scan on a 25-mo-old female patient who presented with opsoclonus myoclonus ataxia syndrome and had negative initial anatomic imaging. The scan showed a somatostatin receptor-overexpressing cervical tumor in favor of a cervical neuroendocrine tumor, with subsequent histopathologic findings of ganglioneuroblastoma.

Detection of acute myocarditis by ECG-triggered PET imaging of somatostatin receptors compared to cardiac magnetic resonance: preliminary results.

Somatostatin receptors are overexpressed by inflammatory cells but not by cardiac cells, under normal conditions. This study assesses the detection of acute myocarditis by the ECG-triggered digital-PET imaging of somatostatin receptors (68Ga-DOTATOC-PET), as compared to Cardiac Magnetic Resonance (CMR) imaging, which is the reference diagnostic method in this setting. METHODS: Fourteen CMR-defined acute myocarditis patients had a first 15-minutes ECG-triggered 68Ga-DOTATOC PET recording, 4.4 ± 3.0 days from peak troponin, and 10 had a second 4.3 ± 0.3 months later. Myocardial/blood SUVmax ratio was analyzed relative to the normal upper limit of 2.18, which had been previously determined from oncology 68Ga-DOTATOC-PET recordings of patients with a similar age range as the myocarditis patients. RESULTS: An increased myocardial 68Ga-DOTATOC uptake relative to blood activity was invariably observed during the acute phase. SUVmax ratio exceeded 2.18 in all patients during the acute phase but also in 3/10 patients at 4-months, at a time when there were no more signs of active inflammation on CMR. A residual myocardial 68Ga-DOTATOC uptake was still observed on all gated-PET cine loops at 4-months. CONCLUSION: These preliminary results suggest that 68Ga-DOTATOC ECG-triggered digital-PET may be as sensitive as CMR at detecting myocarditis during the acute phase and more sensitive at later stages.

Fibromatosis mimicking relapse of a neuroendocrine tumor at 68Ga-DOTATOC positron-emission tomography/computed tomography.

Mesenteric fibromatosis (desmoid tumor) is a locally aggressive fibroblastic lesion, characterized by a high recurrence rate that makes treatment challenging. Currently, there is no evidence-based treatment approach. We report the case of a female patient with a history of neuroendocrine tumor, who underwent 68Ga-DOTATOC positron-emission tomography/computed tomography (PET/CT), showing increased focal abdominal uptake suggestive of disease relapse. Histological examination revealed typical findings of fibromatosis. These findings indicate the expression of staining for somatostatin receptors (SSTRs) on fibromatosis cell surface and suggest to include fibromatosis among the potential causes of false-positive results at 68Ga PET/CT. Moreover, SSTRs expressed in desmoid tumors could be further investigated as a therapeutic target.

Cutting-Edge Imaging of Cardiac Metastases from Neuroendocrine Tumors: Lesson from a Case Series.

With the increasing availability of high-performance medical imaging for the management of patients with neuroendocrine tumors (NETs), a progressive growth of asymptomatic and incidentally detected cardiac metastases (CMs) has been observed in the recent years. In clinical practice, CMs of NENs are often incidentally detected by whole-body 68Ga-labeled somatostatin analogs or 18F-fluorodihydroxyphenylalanine positron emission tomography/computed tomography, and afterwards accurately characterized by cardiac magnetic resonance (CMR) and/or gated cardiac computed tomography when CMR is contraindicated or not available. The interpreting physician should familiarize with the main imaging features of CM, a finding that may be encountered in NETs patients more than previously thought. Herein, we present a case series of four patients with CMs from small-intestine NETs highlighting strengths and weaknesses of a multimodality imaging approach in clinical practice.

18F-DOPA PET/CT at the Forefront of Initial or Presurgical Evaluation of Small-Intestine Neuroendocrine Tumors.

Our objective was to compare the respective value of 68Ga-DOTATOC and 18F-DOPA PET/CT for initial staging or presurgical work-up of patients with small-intestine neuroendocrine tumors (SiNETs). Methods: This was a retrospective, multicenter, noninterventional investigation involving 53 non-surgically treated SiNET patients who underwent both 68Ga-DOTATOC and 18F-DOPA PET/CT within a 6-mo interval without surgical intervention or therapeutic change between the 2 PET/CT studies. Percentage detection rate was calculated according to per-region and per-lesion analyses. Sensitivity for primary tumor detection was assessed in 37 surgically treated patients, taking surgical results (76 SiNETs) as the diagnostic gold standard. Results: 68Ga-DOTATOC PET/CT and 18F-DOPA PET/CT individually identified at least 1 primary SiNET in 92% (34/37) of the patients. Intestinal tumor multifocality was confirmed by histology in 8 patients. 68Ga-DOTATOC and 18F-DOPA PET/CT were concordantly positive for tumor multifocality in 5 patients, discordantly positive in 2 patients, and concordantly negative in 1 patient. The detection rate for subdiaphragmatic nodal metastases on per-region-based analysis was 91% and 98% for 68Ga-DOTATOC and 18F-DOPA PET/CT, respectively (P = 0.18). 18F-DOPA PET/CT detected a higher number of abnormal subdiaphragmatic nodes (P = 0.009). Regarding mesenteric nodes only, 18F-DOPA PET/CT detected more positive regions (P = 0.005) and nodal lesions (P = 0.003) than 68Ga-DOTATOC PET/CT, including nodes at the origin of mesenteric vessels. For detection of distant metastases, 68Ga-DOTATOC and 18F-DOPA PET/CT performed equally well on a per-region-based analysis. As compared with 68Ga-DOTATOC, 18F-DOPA PET/CT detected more hepatic (P < 0.001), peritoneal (P < 0.001), and lung metastases (P < 0.001). Conclusion: 18F-DOPA PET/CT detected more lesions than 68Ga-DOTATOC PET/CT in the studied patients. The respective roles of the two should be discussed in terms of disease staging and treatment selection.

Pindborg Tumor-An Uncommon Odontogenic Tumor Detected by 68Ga-DOTATOC.

A 62-year-old-woman with a suspected Tumor-induced-osteomalacia (TIO), a rare neoplastic syndrome that results in renal phosphate wasting with hypophosphatemia, underwent 68Ga-DOTATOC PET/CT on the suspicion of a mesenchymal tumor producing Fibroblast growth factor 23 (FGF23). Imaging revealed a small osteolytic, somatostatin receptor (SSTR) positive lesion containing calcifications in the alveolar process of the maxilla. No other SSTR-positive focus was found. A biopsy was performed by an oral and maxillofacial surgeon that revealed a calcifying epithelial odontogenic tumor (Pindborg tumor). This case shows that epithelial odontogenic tumors as an uncommon benign tumor entity can also be SSTR-positive.

[68Ga]DOTATOC PET/CT Radiomics to Predict the Response in GEP-NETs Undergoing [177Lu]DOTATOC PRRT: The "Theragnomics" Concept.

Despite impressive results, almost 30% of NET do not respond to PRRT and no well-established criteria are suitable to predict response. Therefore, we assessed the predictive value of radiomics [68Ga]DOTATOC PET/CT images pre-PRRT in metastatic GEP NET. We retrospectively analyzed the predictive value of radiomics in 324 SSTR-2-positive lesions from 38 metastatic GEP-NET patients (nine G1, 27 G2, and two G3) who underwent restaging [68Ga]DOTATOC PET/CT before complete PRRT with [177Lu]DOTATOC. Clinical, laboratory, and radiological follow-up data were collected for at least six months after the last cycle. Through LifeX, we extracted 65 PET features for each lesion. Grading, PRRT number of cycles, and cumulative activity, pre- and post-PRRT CgA values were also considered as additional clinical features. [68Ga]DOTATOC PET/CT follow-up with the same scanner for each patient determined the disease status (progression vs. response in terms of stability/reduction/disappearance) for each lesion. All features (PET and clinical) were also correlated with follow-up data in a per-site analysis (liver, lymph nodes, and bone), and for features significantly associated with response, the Δradiomics for each lesion was assessed on follow-up [68Ga]DOTATOC PET/CT performed until nine months post-PRRT. A statistical system based on the point-biserial correlation and logistic regression analysis was used for the reduction and selection of the features. Discriminant analysis was used, instead, to obtain the predictive model using the k-fold strategy to split data into training and validation sets. From the reduction and selection process, HISTO_Skewness and HISTO_Kurtosis were able to predict response with an area under the receiver operating characteristics curve (AUC ROC), sensitivity, and specificity of 0.745, 80.6%, 67.2% and 0.722, 61.2%, 75.9%, respectively. Moreover, a combination of three features (HISTO_Skewness; HISTO_Kurtosis, and Grading) did not improve the AUC significantly with 0.744. SUVmax, however, could not predict the response to PRRT (p = 0.49, AUC 0.523). The presented preliminary "theragnomics" model proved to be superior to conventional quantitative parameters to predict the response of GEP-NET lesions in patients treated with complete [177Lu]DOTATOC PRRT, regardless of the lesion site.

A Rare Case of Incidental Finding of Cervical Spinal Cord Hemangioblastoma by 68Ga-DOTATOC Positron Emission Tomography/Computed Tomography Scan.

Hemangioblastomas are rare vascular tumors of the central nervous system usually related to other pathological conditions, such as Von Hippel Lindau Syndrome (VHLS) and polycythemia. We describe a case of a 65-year-old man with a neuroendocrine tumor of the ileum presenting with cervical pain who underwent a 68Ga-DOTATOC positron emission tomography/computed tomography (PET/CT) scan that incidentally underlines the presence of hemangioblastoma of the cervical spinal cord. The patient does not have a family history of VHLS nor does he suffer from polycythemia and he is currently waiting for genetic testing. Despite being rare, hemangioblastomas could be possible findings of central nervous system incidentaloma at 68Ga-DOTATOC PET/CT scan, especially in patients with anamnesis with possible related condition.

Incidental cardiac findings on somatostatin receptor PET/CT: What do they indicate and are they of clinical relevance?

We present the case of a 47-year-old man with a history of recurrent episodes of frontal headache, fever, and chest discomfort as well as longstanding, difficult to treat arterial hypertension. Clinical work-up revealed the unexpected finding of an underlying pheochromocytoma as well as recent "silent" myocardial infarction. Our case highlights the importance of paying attention to incidental cardiac findings on somatostatin receptor positron emission tomography/computed tomography, as routinely performed in patients with clinically suspected neuroendocrine tumors. These incidental cardiac findings cannot only indicate a primary or secondary (metastatic) neuroendocrine tumor, but also areas of myocardial inflammation, as somatostatin receptors cannot only be found on the majority of neuroendocrine tumors, but also among other tissues on the surface of activated macrophages and lymphocytes. The detection of myocardial inflammation is of clinical importance and its underlying etiology should be evaluated to prompt eventual necessary treatment, as it is a potential driving force for cardiac remodeling and poor prognosis.

Dual-Tracer (68Ga-DOTATOC and 18F-FDG-)-PET/CT Scan and G1-G2 Nonfunctioning Pancreatic Neuroendocrine Tumors: A Single-Center Retrospective Evaluation of 124 Nonmetastatic Resected Cases.

INTRODUCTION: The combined use of 68gallium (68Ga)-DOTA-peptides and 18fluorine-fluoro-2-deoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) scans in the workup of pancreatic neuroendocrine tumors (PanNETs) is controversial. This study aimed at assessing both tracers' capability to identify tumors and to assess its association with pathological predictors of recurrence. METHODS: Prospectively collected, preoperative, dual-tracer PET/CT scan data of G1-G2, nonmetastatic, PanNETs that underwent surgery between January 2013 and October 2019 were retrospectively analyzed. RESULTS: The final cohort consisted of 124 cases. There was an approximately equal distribution of males and females (50.8%/49.2%) and G1 and G2 tumors (49.2%/50.8%). The disease was detected in 122 (98.4%) and 64 (51.6%) cases by 68Ga-DOTATOC and by 18F-FDG PET/CT scans, respectively, with a combined sensitivity of 99.2%. 18F-FDG-positive examinations found G2 tumors more often than G1 (59.4 vs. 40.6%; p = 0.036), and 18F-FDG-positive PanNETs were larger than negative ones (median tumor size 32 mm, interquartile range [IQR] 21 vs. 26 mm, IQR 20; p = 0.019). The median Ki67 for 18F-FDG-positive and -negative examinations was 3 (IQR 4) and 2 (IQR 4), respectively (p = 0.029). At least 1 pathological predictor of recurrence was present in 74.6% of 18F-FDG-positive cases (vs. 56.7%; p = 0.039), whereas this was not found when dichotomizing the PanNETs by their dimensions (≤/>20 mm). None of the 2 tracers predicted nodal metastasis. The receiver operating characteristic curve analysis showed that 18F-FDG uptake higher than 4.2 had a sensitivity of 49.2% and specificity of 73.3% for differentiating G1 from G2 (AUC = 0.624, p = 0.009). CONCLUSION: The complementary adoption of 68Ga-DOTATOC and 18F-FDG tracers may be valuable in the diagnostic workup of PanNETs despite not being a game-changer for the management of PanNETs ≤20 mm.

Prognostic Value of Whole-Body PET Volumetric Parameters Extracted from 68Ga-DOTATOC PET/CT in Well-Differentiated Neuroendocrine Tumors.

Our objective was to evaluate the prognostic value of somatostatin receptor tumor burden on 68Ga-DOTATOC PET/CT in patients with well-differentiated (WD) neuroendocrine tumors (NETs). Methods: We retrospectively analyzed the 68Ga-DOTATOC PET/CT scans of 84 patients with histologically confirmed WD NETs (51 grade 1, 30 grade 2, and 3 grade 3). For each PET/CT scan, all 68Ga-DOTATOC-avid lesions were independently segmented by 2 operators using a customized threshold based on the healthy liver SUVmax (LIFEx, version 5.1). Somatostatin receptor-expressing tumor volume (SRETV) and total lesion somatostatin receptor expression (TLSRE = SRETV × SUVmean) were extracted for each lesion, and then whole-body SRETV and TLSRE (SRETVwb and TLSREwb, respectively) were defined as the sum of SRETV and TLSRE, respectively, for all segmented lesions in each patient. Time to progression (TTP) was defined as the combination of disease-free survival in patients undergoing curative surgery (n = 10) and progression-free survival for patients with unresectable or metastatic disease (n = 74). TTP and overall survival were calculated by Kaplan-Meier analysis, log-rank testing, and the Cox proportional-hazards regression model. Results: After a median follow-up of 15.5 mo, disease progression was confirmed in 35 patients (41.7%) and 14 patients died. A higher SRETVwb (>39.1 cm3) and TLSREwb (>306.8 g) correlated significantly with a shorter median TTP (12 mo vs. not reached; P < 0.001). In multivariate analysis, SRETVwb (P = 0.005) was the only independent predictor of TTP regardless of histopathologic grade and TNM staging. Conclusion: According to our results, SRETVwb and TLSREwb extracted from 68Ga-DOTATOC PET/CT could predict TTP or overall survival and might have important clinical utility in the management of patients with WD NETs.

Value of 68Ga-DOTATOC and Carbidopa-Assisted 18F-DOPA PET/CT for Insulinoma Localization.

Our objective was to assess the value of 68Ga-DOTATOC and carbidopa-assisted 18F-fluorodihydroxyphenylalanine (18F-DOPA) in 21 hypoglycemic patients. Methods: All patients who underwent 68Ga-DOTATOC or carbidopa-assisted 18F-DOPA PET/CT for suspicion of insulinoma from January 2019 to January 2021 were retrospectively analyzed. A final diagnosis of insulinoma was determined by pathologic reports or consensus. Results: During the study period, 21 patients underwent both 68Ga-DOTATOC and 18F-DOPA PET/CT. A final diagnosis of insulin-secreting tumor was reached in 12 cases, including 11 insulinomas and 1 small mixed neuroendocrine/nonneuroendocrine neoplasm. 18F-DOPA and 68Ga-DOTATOC PET/CT were positive in 5 (45%) and 7 (64%) of 11 cases, respectively, with 4 concordant positive findings. Moreover, 1 insulinoma was visualized exclusively by 18F-DOPA PET/CT and 3 by 68Ga-DOTATOC PET/CT only. 18F-DOPA and 68Ga-DOTATOC PET/CT were falsely positive in 1 nonfunctioning pancreatic neuroendocrine tumor. Conclusion: When 68Ga-exendin-4 is not available, 68Ga-somatostatin receptor PET/CT should be the first choice for insulinoma functional imaging.

A Case of Glomus Tumor Mimicking Neuroendocrine Tumor on 68 Ga-DOTATOC PET/CT.

68 Ga-DOTA-peptide PET/CT is a valuable tool for diagnosing neuroendocrine tumors (NET). Various tumors and normal human tissue express the somatostatin receptor (SSTR), warranting attention to positive findings on 68 Ga-DOTA-peptide PET/CT. However, overexpression of SSTR in glomus tumors has not yet been reported. Gastric glomus tumors show many similar features of NET and are often misdiagnosed. We present the case of a 61-year-old male with a glomus tumor who underwent distal gastrectomy under the pretense of an NET grade 1 because the nodule showed focal intense uptake on preoperative 68 Ga-DOTATOC PET/CT.

Receptor depletion and recovery in small-intestinal neuroendocrine tumors and normal tissues after administration of a single intravenous dose of octreotide measured by 68Ga-DOTATOC PET/CT.

BACKGROUND: Low-grade neuroendocrine tumors (NETs) are characterized by an abundance of somatostatin receptors (SSTR) that can be targeted with somatostatin analogs (SSA). When activated with a single dose of SSA, the receptor-ligand complex is internalized, and the receptor is by default recycled within 24 h. Ongoing medication with long-acting SSAs at 68Ga-DOTA-SSA-PET has been shown to increase the tumor-to-normal organ contrast. This study was performed to investigate the time-dependent extended effect (7 h) of a single intravenous dose of 400 µg short-acting octreotide on the tumor versus normal tissue uptake of 68Ga-DOTATOC. METHODS: Patients with small-intestinal NETs received a single intravenous dose of 400 µg octreotide and underwent dynamic abdominal 68Ga-DOTATOC-PET/CT at three sessions (0, 3 and 6 h) plus static whole-body (WB) PET/CT (1, 4 and 7 h), starting each PET/CT session by administering 167 ± 21 MBq, 23.5 ± 4.2 µg (mean ± SD, n = 12) of 68Ga-DOTATOC. A previously acquired clinical whole-body 68Ga-DOTATOC scan was used as baseline. SUV and net uptake rate Ki were calculated in tumors, and SUV in healthy organs. RESULTS: Tumor SUV decreased significantly from baseline to 1 h post-injection but subsequently increased over time and became similar to baseline at 4 h and 7 h. The tumor net uptake rate, Ki, similarly increased significantly over time and showed a linear correlation both with SUV and tumor-to-blood ratio. By contrast, the uptake in liver, spleen and pancreas remained significantly below baseline levels also at 7 h and the receptor turn-over in tumors thus exceeded that in the normal tissue, with restitution of tumor 68Ga-DOTATOC uptake mainly completed at 7 h. These results however differed depending on tumor size, with significant increases in Ki and SUV between the 1st and 2nd PET, in large tumors (≥ 4 mL) but not in small (> 1 to < 4 mL) tumors. CONCLUSION: SSTR recycling is faster in small-intestinal NETs than in liver, spleen and pancreas. This opens the possibility to protect normal tissues during PRRT by administering a single dose of cold peptide hours before peptide receptor radionuclide therapy (PRRT), and most likely additionally improve the availability and uptake of the therapeutic preparation in the tumors.