Radiotracer Uptake Research Articles

Pre-symptomatic scintigraphic and genetic cascade screening in cardiac transthyretin amyloidosis.

While early diagnosis is crucial, as new treatments can significantly slow the progression of the disease, there is growing evidence on the application of novel imaging techniques for detecting transthyretin amyloidosis (ATTR) in pre-symptomatic stages. This study aimed to evaluate the utility of pre-symptomatic scintigraphic imaging cascade screening for early detection of ATTR. During the period from 2020 to 2024, we conducted a prospective study that enrolled 100 consecutive adults. The study utilized a multimodal cascade screening approach to assess asymptomatic relatives of individuals with ATTR (ClinicalTrials.gov Identifier: NCT05814380). The analysis incorporated clinical data, genetic testing, echocardiography, scintigraphy and single-photon emission computed tomography/computed tomography (SPECT/CT) with [99mTc]Tc-DPD, regardless of the predicted age of disease onset. Overall, scintigraphy identified cardiac amyloidosis (CA) in 8.2% of relatives, while 20.5% carried a pathogenic transthyretin variant without radiotracer uptake, with Phe53Leu being predominant. Notably, no relatives of wild-type ATTR patients exhibited CA on scintigraphy or carried a transthyretin variant. Additionally, newly-diagnosed relatives with ATTR CA presented elevated high-sensitivity troponin levels and exhibited a higher incidence of pathological electrocardiographic Q waves, greater thickness of the intraventricular septum and left ventricular posterior wall, a notable decline in lateral wall and intraventricular septal E' tissue velocities measured by TDI, and the "5-5-5" sign (p < 0.05). The presented findings demonstrate that implementing a systematic screening protocol, which integrates genetic and scintigraphic testing, facilitates the early detection of ATTR. Crucially, a significant proportion of asymptomatic relatives of patients with hereditary ATTR may suffer from underlying CA. ClinicalTrials.gov Identifier: NCT05814380.

Immuno-PET Imaging of CD93 Expression with 64Cu-Radiolabeled NOTA-mCD93 ([64Cu]Cu-NOTA-mCD93) and Insulin-Like Growth Factor Binding Protein 7 ([64Cu]Cu-NOTA-IGFBP7).

CD93 is overexpressed in multiple solid tumor types, serving as a novel target for antiangiogenic therapy. The goal of this study was to develop a 64Cu-based positron emission tomography (PET) tracer for noninvasive imaging of CD93 expression. Antimouse-CD93 mAb (mCD93) and the CD93 ligand IGFBP7 were conjugated to a bifunctional chelator, p-isothiocyanatobenzyl-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-NOTA) and labeled with 64Cu. To evaluate the pharmacokinetic properties and tumor-targeting efficacy of [64Cu]Cu-NOTA-mCD93 and [64Cu]Cu-NOTA-IGFBP7, PET imaging and biodistribution were performed on both 4T1 murine breast tumor-bearing mice and MDA-MB-231 human breast tumor-bearing mice. The tumor model HT1080-FAP, which does not overexpress CD93, was used as a negative control. Fluorescent immunostaining was conducted on different tissues to correlate radiotracer uptake with CD93 expression. 64Cu-labeling was achieved with high yield and specific activity. Serial PET imaging revealed that the in vivo performance of [64Cu]Cu-NOTA-IGFBP7 was superior to that of [64Cu]Cu-NOTA-mCD93, and that the tracer [64Cu]Cu-NOTA-IGFBP7 exhibited elevated tumor uptake values and excellent tumor retention in MDA-MB-231 mice, rather than in 4T1 murine mice. The MDA-MB-231 tumor uptake of [64Cu]Cu-NOTA-IGFBP7 was 2.85 ± 0.15, 3.69 ± 0.60, 6.91 ± 0.88, and 6.35 ± 0.55%ID/g at 1, 4, 24, and 48 h p.i., respectively, which were significantly higher than that in the CD93-negative HT1080-FAP tumor (0.73 ± 0.15, 0.97 ± 0.31, 1.00 ± 0.07, and 1.02 ± 0.11%ID/g, respectively). The significant difference between positive and negative tumors indicated [64Cu]Cu-NOTA-IGFBP7 was specifically binding to CD93. Biodistribution data as measured by gamma counting were consistent with the PET analysis. Ex vivo histology further confirmed the high CD93 expression on MDA-MB-231 tumor tissues. Herein, we prepared two novel radiotracers, [64Cu]Cu-NOTA-mCD93 and [64Cu]Cu-NOTA-IGFBP7, for the first immune-PET imaging of CD93 expression. Our results suggest that [64Cu]Cu-NOTA-IGFBP7 is a more potential radiotracer for visualizing angiogenesis due to its sensitive, persistent, and CD93-specific characteristics.

BIOM-20. EVALUATING THE POTENTIAL OF PSMA TARGETING IN CNS TUMORS: INSIGHTS FROM LARGE-SCALE TRANSCRIPTOME PROFILING

Abstract PURPOSE Prostate-specific membrane antigen (PSMA) is a well-established target in prostate cancer therapy that has shown potential as a theranostic target across non-central nervous system (CNS) and CNS tumor types. We aimed to investigate the pan-tissue expression pattern of the PSMA-encoding gene FOLH1 to assess whether transcriptome profiling can inform tumor theranostics. EXPERIMENTAL DESIGN We assessed FOLH1 expression from the Open Pediatric Cancer Project (OpenPedCan, n = 2132 specimens), The Cancer Genome Atlas (TCGA, n = 10411 specimens), and the Genotype Tissue Expression Project (GTEx, n = 17382 specimens) in relation to published reports of PSMA radionuclide uptake. RESULTS When comparing FOLH1 expression across tumor versus normal tissues, we found that non-CNS tumors exhibiting elevated expression of at least two-fold (FDR &amp;lt; 0.05) were reported to have successful PSMA radionuclide uptake in contrast to tumors with less than a two-fold elevation or with lower expression of FOLH1 relative to normal. Notably, CNS tumors universally exhibited lower expression of FOLH1 relative to normal brain tissue, but we observed considerable variation in the expression of blood-tumor barrier (BTB) components associated with reports of BTB integrity and uptake of PSMA radiotracers. CONCLUSIONS Large-scale transcriptomics data may help guide the application of PSMA-based radionuclide therapies in non-CNS tumors, but care should be taken to account for BTB effects in CNS tumors when assessing the potential for radionuclide success. Our analysis demonstrated that FOLH1 showed a lack of tumor-specific expression for both adult and pediatric CNS tumors when compared to normal brain tissue, suggesting that PSMA is not a desirable target in this disease type. This study highlights the utility of utilizing large-scale molecular data to guide the selection of theranostic targets.

NIMG-14. HEAD-TO-HEAD COMPARISON OF18F-FET PET AND68GA-PSMA-11 PET IN DISTINGUISHING SMALL VOLUME TUMOR PROGRESSION VS TREATMENT-RELATED CHANGE IN POST-STANDARD OF CARE TREATMENT OF HIGH-GRADE GLIOMA USING DYNAMIC ACQUISITION AND KINETIC MODELING

Abstract BACKGROUND The inability to accurately distinguish between tumor progression and treatment-related changes in patients with high-grade glioma on routine imaging can negatively impact patient management and in some cases, outcome. Various imaging methods have been used to address this issue, including 18F-fluoro-ethyl-tyrosine (FET) PET and MR perfusion. However, these methods may not provide reliable results in cases of small lesion size or hemorrhage within the treatment site. The prostate-specific membrane antigen (PSMA) has been observed to be expressed by neovasculature in brain tumors. Since PSMA cannot cross the blood brain barrier, uptake of PSMA in the brain carries high-level of suspicion for residual tumor. Still, further work is needed to better understand PSMA uptake in the tumor bed following standard of care (SOC) treatment and to compare to currently available neuro-oncologic radiotracers, such as FET. We hypothesize that PSMA imaging of glioma neovasculature will provide unique diagnostic information that will aid in the differentiation of small volume tumor progression from treatment-related changes in the post-SOC treatment setting. METHODS Patients who underwent clinical Expanded Access PET/MR imaging with 18F-FET were re-imaged in a research protocol that collected a brain 68Ga-PSMA-11 PET/CT scan, as well as a repeat 18F-FET PET/CT. Kinetic modeling of dynamic radiotracer uptake was performed. Scans were assessed for correlation with subsequent imaging and changes in clinical management. RESULTS All PSMA scans that were performed were concordant with the initial clinical FET scan, subsequent imaging follow up and appropriate changes in clinical management. The PSMA-detected site was confirmed to be tumor in a single case with subsequent tissue sampling. One patient who was started on bevacizumab after their clinical FET demonstrated a significant decrease in uptake on the research FET scan, but persistent uptake on PSMA. CONCLUSION PSMA may effectively show tumor recurrence in post-SOC treatment high-grade glioma patients.

Shifts in the spatiotemporal profile of inflammatory phenotypes of innate immune cells in the rat brain following acute intoxication with the organophosphate diisopropylfluorophosphate

Acute intoxication with cholinesterase inhibiting organophosphates (OP) can produce life-threatening cholinergic crisis and status epilepticus (SE). Survivors often develop long-term neurological consequences, including spontaneous recurrent seizures (SRS) and impaired cognition. Numerous studies implicate OP-induced neuroinflammation as a pathogenic mechanism contributing to these chronic sequelae; however, little is known about the inflammatory phenotype of innate immune cells in the brain following acute OP intoxication. Thus, the aim of this study was to characterize the natural history of microglial and astrocytic inflammatory phenotypes following acute intoxication with the OP, diisopropylfluorophosphate (DFP). Adult male and female Sprague–Dawley rats were administered a single dose of DFP (4 mg/kg, sc) followed by standard medical countermeasures. Within minutes, animals developed benzodiazepine-resistant SE as determined by monitoring seizures using a modified Racine scale. At 1, 3, 7, 14, and 28 d post-exposure (DPE), neuroinflammation was assessed using translocator protein (TSPO) positron emission tomography (PET) and magnetic resonance imaging (MRI). In both sexes, we observed consistently elevated radiotracer uptake across all examined brain regions and time points. A separate group of animals was euthanized at these same time points to collect tissues for immunohistochemical analyses. Colocalization of IBA-1, a marker for microglia, with iNOS or Arg1 was used to identify pro- and anti-inflammatory microglia, respectively; colocalization of GFAP, a marker for astrocytes, with C3 or S100A10, pro- and anti-inflammatory astrocytes, respectively. We observed shifts in the inflammatory profiles of microglia and astrocyte populations during the first month post-intoxication, largely in hyperintense inflammatory lesions in the piriform cortex and amygdala regions. In these areas, iNOS+ proinflammatory microglial cell density peaked at 3 and 7 DPE, while anti-inflammatory Arg1+ microglia cell density peaked at 14 DPE. Pro- and anti-inflammatory astrocytes emerged within 7 DPE, and roughly equal ratios of C3+ pro-inflammatory and S100A10+ anti-inflammatory astrocytes persisted at 28 DPE. In summary, microglia and astrocytes adopted mixed inflammatory phenotypes post-OP intoxication, which evolved over one month post exposure. These activated cell populations were most prominent in the piriform and amygdala areas and were more abundant in males compared to females. The temporal relationship between microglial and astrocytic responses suggests that initial microglial activity may influence delayed, persistent astrocytic responses. Further, our findings identify putative windows for inhibition of OP-induced neuroinflammatory responses in both sexes to evaluate the therapeutic benefit of anti-inflammation in this context.

A series of cases of transthyretin amyloid cardiomyopathy with negative bone scintigraphy but a confirmed positive endomyocardial biopsy

BackgroundBone scintigraphy (BS) is established as an accurate, non-invasive method for the diagnosis of transthyretin amyloid cardiomyopathy (ATTR-CM). In a real-life setting, however, some patients with no cardiac uptake on BS turn out to have cardiac-biopsy-confirmed ATTR-CM. We retrospectively included all patients diagnosed at the French Referral Center for ATTR-CM and who had data for BS and a cardiac biopsy.ResultsOf 271 patients with positive cardiac biopsy, 14 (5%) had no cardiac uptake on 99mTc-hydroxymethylene diphosphonate BS. Cardiac uptake was found in four of the seven patients who had a second BS assessment with 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD). A retrospective review of the BS data found low cardiac uptake in four patients (two with HMDP and two with both radiotracers). Ultimately, six of the 14 patients with a biopsy-confirmed diagnosis of ATTR-CM did not show any cardiac radiotracer uptake.ConclusionsAn endomyocardial biopsy may be necessary for confirming the diagnosis of ATTR-CM in patients with clinical and imaging signs of cardiac amyloidosis but no cardiac radiotracer uptake in BS.

D-[5-11C]-Glutamine Positron Emission Tomography Imaging for Diagnosis and Therapeutic Monitoring of Orthopedic Implant Infections.

Orthopedic implant infections (OIIs) present diagnostic and therapeutic challenges, owing to the lack of methods to distinguish between active infection and sterile inflammation. To address this unmet need, d-amino-acid-based radiotracers with unique metabolic profiles in microorganisms have emerged as a novel class of infection-specific imaging agents. Given the pivotal role of d-glutamine in bacterial biofilm formation and virulence, herein, we explored the potential of positron emission tomography (PET) imaging with d-[5-11C]-Glutamine (d-[5-11C]-Gln) for early detection and treatment monitoring of OIIs. In vitro studies confirmed an active uptake of d-[5-11C]-Gln by Staphylococcus aureus (S. aureus) biofilm commonly associated with OIIs. In vivo evaluations included PET imaging comparisons with d-[5-11C]-Gln vs l-[5-11C]-Gln or 2-deoxy-2-[18F]-fluoroglucose ([18F]-FDG) in a rat OII model with tibial implantation of sterile or S. aureus-colonized stainless-steel screws before and after treatment. These studies demonstrated that the uptake of d-[5-11C]-Gln was significantly higher in the infected screws than that in sterile screws (∼3.4-fold, p = 0.008), which displayed significantly higher infection-to-background muscle uptake ratios (∼2-fold, p = 0.011) with d-[5-11C]-Gln as compared to l-[5-11C]-Gln. Following a 3 week vancomycin treatment, imaging with d-[5-11C]-Gln showed a significant reduction in uptake at the infected sites (∼3-fold, p = 0.0008). Further regression analyses revealed a superior correlation of residual infection-associated radiotracer uptake with the postimaging ex vivo bacterial counts for d-[5-11C]-Gln (k = 0.473, R2 = 0.796) vs [18F]-FDG (k = 0.212, R2 = 0.434), suggesting that d-[5-11C]-Gln PET had higher sensitivity for detecting residual bacterial burden than [18F]-FDG PET. Our results demonstrate the translational potential of d-[5-11C]-Gln PET imaging for noninvasive detection and treatment monitoring of OIIs.

Clinical value of SUVpeak-to-tumor centroid distance on FDG PET/CT for predicting neoadjuvant chemotherapy response in patients with breast cancer

BackgroundSince it has been found that the maximum metabolic activity of a cancer lesion shifts toward the lesion edge during cancer progression, normalized distances from the hot spot of radiotracer uptake to tumor centroid (NHOC) and tumor perimeter (NHOP) have been suggested as novel F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) parameters that can reflect cancer aggressiveness. This study aimed to investigate whether NHOC and NHOP parameters could predict pathological response to neoadjuvant chemotherapy (NAC) and progression-free survival (PFS) in breast cancer patients.MethodsThis study retrospectively enrolled 135 female patients with breast cancer who underwent pretreatment FDG PET/CT and received NAC and subsequent surgical resection. From PET/CT images, normalized distances of maximum SUV and peak SUV-to-tumor centroid (NHOCmax and NHOCpeak) and -to-tumor perimeter (NHOPmax and NHOPpeak) were measured, in addition to conventional PET/CT parameters.ResultsOf 135 patients, 32 (23.7%) achieved pathological complete response (pCR), and 34 (25.2%) had events during follow-up. In the receiver operating characteristic (ROC) curve analysis, NHOCmax showed the highest area under the ROC curve value (0.710) for predicting pCR, followed by NHOCpeak (0.694). In the multivariate logistic regression analysis, NHOCmax, NHOCpeak, and NHOPmax were independent predictors for pCR (p < 0.05). In the multivariate survival analysis, NHOCpeak (p = 0.026) was an independent predictor for PFS along with metabolic tumor volume, with patients having higher NHOCpeak showing worse PFS.ConclusionNHOCpeak on pretreatment FDG PET/CT could be a potential imaging parameter for predicting NAC response and survival in patients with breast cancer.

Superscan Pattern on Bone Scintigraphy: A Comprehensive Review

Background/Objectives: The superscan pattern is a characteristic finding on bone scintigraphy, associated with a variety of metabolic bone diseases, malignancies, and other conditions. This pattern is characterized by a diffuse and intense uptake of radiotracer throughout the entire skeleton. Despite being a relatively rare finding, the superscan pattern can have significant clinical implications. Methods: This comprehensive review summarizes the available literature on the superscan pattern, focusing on its pathophysiology, clinical significance, and differential diagnoses. Relevant studies and case reports were analyzed to outline the diagnostic challenges associated with the interpretation of bone scintigraphy featuring the superscan pattern. Results: The literature highlights the clinical significance of the superscan pattern in various metabolic and oncologic conditions. Misinterpretation of this pattern can lead to diagnostic challenges, especially in distinguishing it from other pathologic conditions. Differential diagnosis remains crucial in the accurate interpretation and subsequent management of patients with this finding. Conclusions: This review provides a comprehensive overview of the superscan pattern on bone scintigraphy, aiming to assist clinicians in recognizing and managing this rare yet clinically important finding.

6421 Imaging Phenotype May Predict Genotype In Human Pheochromocytoma: Relationships Between Genetic Mutation Clusters, Metabolite Transporter Expression, And Radiotracer Uptake

Abstract Disclosure: I. Sakuma: None. M. Fujimoto: None. D.F. Vatner: None. K. Yokote: None. T. Tanaka: None. Context [1]23I-metaiodobenzylguanidine scintigraphy (MIBG) and [1]8F-fluoro-2-doxy-D-glucose positron emission tomography (FDG-PET) are helpful for the localization of pheochromocytoma. The norepinephrine transporter (NET) and the glucose transporter 1 (GLUT1) are thought to be critical for the uptake of these radioisotopes. NET expression is activated by Paired Like Homeobox (PHOX2) and glucocorticoid receptor (GR) in neuroblastoma cells. Around 70% of pheochromocytomas carry well-known mutations. Pheochromocytoma-associated genes are divided into two clusters: the pseudohypoxia-related cluster 1 and the kinase signaling-related cluster 2. Cluster 1 mutation are associated with noradrenergic pheochromocytomas with an elevated metastatic risk. Cluster 2 tumors demonstrate an adrenergic phenotype with a less aggressive course. How mutations of cluster 1 and cluster 2 impact the expression of NET/GLUT1 and on radiotracer uptake remains unclear. Hypothesis Cluster 1 and cluster 2 will have different effects on the expression of transcription factors associated with chromaffin cell differentiation with resultant differential effects on NET/GLUT1 expression. Methods 42 patients with pheochromocytoma were evaluated by MIBG and FDG-PET. Tumor gene expression was evaluated by real-time qPCR, and mutation analyses were performed by Sanger or next-generation sequencing. Results 88% of tumors were MIBG-avid, and 67% were FDG-avid. The expression of NET in MIBG-negative tumors was 70% lower than in MIBG-positive tumors. The expression of GLUT1 in FDG-PET-negative tumors was 75% lower than in FDG-PET-positive tumors. The expression of NET positively correlated with transcription factors involved in chromaffin cell maturation, including PHOX2A, PHOX2B, GATA binding protein 3 (GATA3), GR, catecholamine synthases, and insulinoma associated 1 (INSM1). The JASPAR database for promoter analysis revealed putative responsive regions of the transcription factors PHOX2A, PHOX2B, GATA3, GR, and INSM1 on the NET gene. Seven patients (16.7%) had mutations in cluster 1, and fourteen patients (33.3%) had mutations in cluster 2. Cluster 2 exhibited elevated NET, PHOX2A, PHOX2B, GATA3, GR, and INSM1 expression levels compared to cluster 1. Cluster 1 showed a higher expression level of GLUT1 and BMP4 that is associated with early chromaffin cell differentiation. Conclusions In pheochromocytomas, MIBG and FDG uptake correlated with the expression levels of NET and GLUT1, respectively. NET expression is associated with chromaffin cell differentiation transcription factor expression. We propose that pheochromocytomas that carry Cluster 1 mutations are more likely to be missed in MIBG due to low NET expression, while pheochromocytomas that carry Cluster 2 mutations are more likely to be missed on FDG-PET due to low GLUT1 expression with a more mature chromaffin cell phenotype. Presentation: 6/2/2024

7204 An Unexpected Cause of Ga-68 Dotatate PET/CT Somatostatin Receptor Avidity in a Pediatric Patient with Hereditary Paraganglioma-Pheochromocytoma Syndrome due to an SDHA Mutation

Abstract Disclosure: K. Leopold: None. S. Polites: None. L. Binkovitz: None. L. Casas: None. A.N. Lteif: None. Title: An Unexpected Cause of Ga-68 Dotatate PET/CT Somatostatin Receptor Avidity in a Pediatric Patient with Hereditary Paraganglioma-Pheochromocytoma Syndrome due to an SDHA Mutation. Introduction: Individuals with Succinate Dehydrogenase (SDHx) gene mutations have an increased risk of paragangliomas and pheochromocytomas beginning in childhood.Clinical Case: A 9 year old male with Cornelia de Lange syndrome and a paternally inherited SDHA pathogenic gene variant (c1534C&amp;gt;T) presented with worsening migraine headaches and skin pallor with activity. 24 hour urine fractionated metanephrines were mildly elevated, with metanephrine 122 mcg/24h (29-92 mcg/24 h), normetanephrine 187 mcg/24 h (34-169 mcg/24 h), and total metanephrine 309 mcg/24 h (47-223 mcg/24 h). Ga-68 DOTATATE PET/CT showed a focus of moderately increased radiotracer activity in the anterior aspect of the distal gastric antrum with a max SUV 8.2 corresponding to a 9x7 mm nodule on CT in the same area, suggestive of underlying somatostatin receptor positive lesion such as a paraganglioma. MRI with contrast completed to further characterize the lesion showed no visible mass corresponding to the focal area of radiotracer uptake on DOTATATE PET/CT. Repeat 24 h urine metanephrines continued to show mild elevation of metanephrine (138 mcg/24h), normetanephrine (200 mcg/24h), and total metanephrines (338 mcg/24h). 24 hour urine catecholamines, 5-Hydroxyindoleacetic acid, and homovanillic acid were normal. An upper endoscopic ultrasound was completed which confirmed the presence of a lesion near the stomach but not arising from the stomach wall and not consistent with a gastrointestinal stromal tumor. CT enterography with IV contrast showed a 6x6 mm enhancing mass within the distal right lateral gastric wall. Due to ongoing symptoms, mild elevations in urine fractionated metanephrines, and a clear mass on US and CT, the patient underwent laparoscopic abdominal exploration where a 14x14x13 mm mass with surrounding gastric and duodenal serosa was excised with primary closure of the bowel. Pathology showed ectopic pancreatic tissue in the wall of the small bowel and stomach. Repeat Ga-68 DOTATATE PET/CT 5 months following surgery showed resolution of the distal gastric somatostatin receptor avidity. Clinical Lesson: This is the first case of ectopic pancreatic tissue mimicking a paraganglioma in a pediatric patient with hereditary paraganglioma-pheochromocytoma syndrome. False positive imaging should be considered in patients with SDHx mutations when the uptake is atypical in location and when the elevation in urine metanephrines is mild. Presentation: 6/3/2024

8769 A Case of Metastatic and Catecholamine Producing Bilateral Pheochromocytoma in a Patient with RET Gene Mutation

Abstract Disclosure: R.A. Mayers: None. A. Szafran-Swietlik: None. RET mutation, observed in multiple endocrine neoplasia type 2 syndromes, is implicated in the development of pheochromocytomas of the kinase signaling cluster. Such tumors have lower metastatic risk and adrenergic production compared to the ones from the other clusters. We present a case of a metastatic, bilateral, small and biochemically active pheochromocytoma .This is the case of a 27-year-old man diagnosed with MEN 2A. He underwent total thyroidectomy due to medullary thyroid carcinoma at 2 years old. He was deemed cured and started on levothyroxine replacement. Since then, his plasma metanephrines by liquid chromatography-mass spectrometry and urine metanephrines done in a yearly basis as screening, were always within range of normality. Over the years, he developed substance abuse disorder with use of Kratom and methamphetamines and was admitted in a rehabilitation center multiple times in the last three years. During this time, the patient was reported to be slightly tachycardiac which was initially attributed to the use of substances. On the last year, an echocardiogram done as evaluation of his tachycardia showed an ejection fraction of 35%. Later, his annual metanephrine levels were markedly elevated (free metanephrine: 137 pg/mL and free normetanephrine : 157 pg/mL, normal ranges reported as less than 57 pg/mL and less than 148 pg/mL respectively). Abdominal tomography showed a right adrenal nodule of 1.2 cm and a left adrenal nodule of 1.6 cm, both with more than 10 Hounsfield Units. A Metaiodobenzylguanidine scan revealed a left adrenal nodule of 1.8 cm with diffuse radiotracer uptake, a right adrenal nodule of 1.2 cm with radiotracer activity and 3 subtle areas of focally increased radiotracer activity in the liver, two in left hepatic lobe and other in posterior right upper lobe. He underwent bilateral adrenalectomy with cortical sparring. Pathology results evidenced a left adrenal with a unifocal mass of 1.8 cm and a right adrenal with a mass of 1.2 cm , both without lymphovascular, capsular, local invasion or necrosis, a mitotic rate of 1-2 without atypical mitosis, not encapsulated with clean margins and positive for synaptophysin , chromogranin and S100 stains. An additional mass of 0.7 cm on the right adrenal gland was described with similar characteristics to the described before except for the involvement of the surgical margins. Currently on the literature there are different opinions regarding screening approach for pheochromocytomas in the presence of RET mutations. There are not strong recommendations regarding the use of imaging as a screening tool in this group of patients. It is important to consider that there are cases, as the one described in this report, that might present metastatic disease even with the presence of small pheochromocytomas that belong to the cluster of kinase signaling. Presentation: 6/3/2024

8104 Rare Case Of Ectopic Cushing’s Syndrome Secondary To Metastatic Parotid Pleomorphic Adenocarcinoma

Abstract Disclosure: B.S. Neutel: None. P. Manroa: None. Background: Pleomorphic adenocarcinoma of the parotid gland is a rare malignancy and ectopic ACTH secretion from these tumors is very rarely described. We report a case of ectopic Cushing’s syndrome (CS) in such a patient and describe the clinical course. Clinical Case: A 69-year-old female with left parotid pleomorphic adenocarcinoma status post surgery and adjuvant radiotherapy presented to her local hospital approximately 7 months after initial treatment with proximal muscle weakness and near-syncope. Workup revealed profound hypokalemia at 1.6 mmol/L (n 3.5-5.3 mmol/L) along with new-onset hypertension (BP 175/110 mm Hg) and hyperglycemia with a HbA1c 6.5 % (n &amp;lt;5.7%), as well as metabolic alkalosis with a bicarbonate level of &amp;gt;40 mmol/L (n 22-32 mmol/L). A CT scan showed multiple liver metastases and a biopsy confirmed metastatic parotid pleomorphic adenocarcinoma. She was then transferred to our comprehensive cancer center for further management. She reported muscle weakness, easy bruising, and facial edema. She denied acne, hirsutism, or abdominal striae. Endocrine workup revealed a random cortisol of 56 mcg/dL (n 3-18 mcg/dL) and ACTH of 378 pg/mL (n 7.2-63.3 pg/mL). Her AM cortisol level remained unsuppressed at 79.2 and 59.4 mcg/dL (n&amp;lt; 1.8 mcg/dL) after 1 mg and 8 mg overnight dexamethasone suppression tests respectively. Late-night salivary cortisol was 7.9 mcg/dL (n &amp;lt;0.112 mcg/dL). An MRI of the sella was negative for any pituitary lesions. After stabilizing her clinical condition and correcting electrolyte abnormalities, she was started on chemotherapy with paclitaxel and carboplatin by the oncologist. Based on clinical suspicion of ectopic CS, ketoconazole was started and titrated upwards with rapid improvement of blood pressure, hypokalemia, and hyperglycemia. She was discharged home and antihypertensives were tapered off. ACTH staining on the liver biopsy was unable to be performed due to paucity of the specimen. A Ga-68-DOTATATE PET CT revealed increased radiotracer uptake in the liver lesion suggestive of SSTR 2 receptor positivity. Despite initial clinical improvement, her disease progressed with widespread liver, lymph node, and osseous metastases within 3 months necessitating escalating doses of ketoconazole, spironolactone, and potassium supplementation. The patient elected to pursue hospice care due to intolerance to chemotherapy and passed away shortly afterward. Conclusion: Although ectopic CS caused by parotid pleomorphic adenocarcinoma is rare, prompt recognition and treatment is necessary because ectopic ACTH production is associated with poor prognosis in these patients. Presentation: 6/3/2024

Prospective Comparison of [18F]FDG and [18F]AIF-FAPI-74 PET/CT in the Evaluation of Potentially Resectable Pancreatic Ductal Adenocarcinoma.

Accurate clinical staging of potentially resectable pancreatic ductal adenocarcinoma (PDAC) is critical for establishing optimal treatment strategies. While the efficacy of fluorine-18-fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) in clinical staging is unclear, PET/CT detecting fibroblast-activation protein (FAP) expression has recently received considerable attention for detecting various tumors, including PDAC, with high sensitivity. We explored the efficacy of [18F]FDG and [18F]AIF-FAPI-74 PET/CT in the initial evaluation of potentially resectable PDAC. Between 2021 and 2022, twenty participants with newly diagnosed potentially resectable PDAC were enrolled. After the initial evaluation with pancreatic CT, [18F]FDG PET/CT, and [18F]AIF-FAPI-74 PET/CT, treatment strategies were determined considering the participant's general status, clinical staging, and resectability. Pathological information from the surgical specimens was only available in 17 participants who underwent curative-intent surgery. Head-to-head comparisons of quantitative radiotracer uptake and diagnostic performance were performed among imaging modalities. [18F]AIF-FAPI-74 PET/CT showed a significantly higher maximum standardized uptake value than [18F]FDG PET/CT did in evaluating primary pancreatic lesions (median [interquartile range]; 12.6 [10.7-13.7] vs. 6.3 [4.8-9.2]; P < 0.001). In contrast, [18F]AIF-FAPI-74 PET/CT showed a significantly lower mean standardized uptake value than [18F]FDG PET/CT did in evaluating background organ (median [interquartile range]) 0.8 [0.7-0.9] vs. 2.6 [2.3-2.7]; P < 0.001). In addition, the sensitivity of [18F]AIF-FAPI-74 PET/CT in detecting metastatic lymph nodes was higher than that of [18F]FDG PET/CT (50.0% vs. 0.0%; P = 0.026). This study demonstrated that [18F]AIF-FAPI-74 PET/CT could improve the clinical staging of potentially resectable PDAC.

An in vivo tumour organoid model based on the chick embryonic chorioallantoic membrane mimics key characteristics of the patient tissue: a proof-of-concept study

BackgroundPatient-derived tumour organoids (PDOs) are highly advanced in vitro models for disease modelling, yet they lack vascularisation. To overcome this shortcoming, organoids can be inoculated onto the chorioallantoic membrane (CAM); the highly vascularised, not innervated extraembryonic membrane of fertilised chicken eggs. Therefore, we aimed to (1) establish a CAM patient-derived xenograft (PDX) model based on PDOs generated from the liver metastasis of a colorectal cancer (CRC) patient and (2) to evaluate the translational pipeline (patient – in vitro PDOs – in vivo CAM-PDX) regarding morphology, histopathology, expression of C-X-C chemokine receptor type 4 (CXCR4), and radiotracer uptake patterns.ResultsThe main liver metastasis of the CRC patient exhibited high 2-[18F]FDG uptake and moderate and focal [68Ga]Ga-Pentixafor accumulation in the peripheral part of the metastasis. Inoculation of PDOs derived from this region onto the CAM resulted in large, highly viable, and extensively vascularised xenografts, as demonstrated immunohistochemically and confirmed by high 2-[18F]FDG uptake. The xenografts showed striking histomorphological similarity to the patient’s liver metastasis. The moderate expression of CXCR4 was maintained in ovo and was concordant with the expression levels of the patient’s sample and in vitro PDOs. Following in vitro re-culturing of CAM-PDXs, growth, and [68Ga]Ga-Pentixafor uptake were unaltered compared to PDOs before transplantation onto the CAM. Although [68Ga]Ga-Pentixafor was taken up into CAM-PDXs, the uptake in the baseline and blocking group were comparable and there was only a trend towards blocking.ConclusionsWe successfully established an in vivo CAM-PDX model based on CRC PDOs. The histomorphological features and target protein expression of the original patient’s tissue were mirrored in the in vitro PDOs, and particularly in the in vivo CAM-PDXs. The [68Ga]Ga-Pentixafor uptake patterns were comparable between in vitro, in ovo and clinical data and 2-[18F]FDG was avidly taken up in the patient’s liver metastasis and CAM-PDXs. We thus propose the CAM-PDX model as an alternative in vivo model with promising translational value for CRC patients.Graphical

Visualizing Immune Checkpoint Inhibitors Derived Inflammation in Atherosclerosis.

Immune checkpoint inhibitor (ICI) usage has resulted in immune-related adverse events in patients with cancer, such as accelerated atherosclerosis. Of immune cells involved in atherosclerosis, the role of CCR2+ (CC motif chemokine receptor 2-positive) proinflammatory macrophages is well documented. However, there is no noninvasive approach to determine the changes of these cells in vivo following ICI treatment and explore the underlying mechanisms of immune-related adverse events. Herein, we aim to use a CCR2 (CC motif chemokine receptor 2)-targeted radiotracer and positron emission tomography (PET) to assess the aggravated inflammatory response caused by ICI treatment in mouse atherosclerosis models and explore the mechanism of immune-related adverse events. Apoe-/- mice and Ldlr-/- mice were treated with an ICI, anti-PD1 (programmed cell death protein 1) antibody, and compared with those injected with either isotype control IgG or saline. The radiotracer 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-ECL1i (extracellular loop 1 inverso) was used for PET imaging of CCR2+ macrophages. Atherosclerotic arteries were collected for molecular characterization. CCR2 PET revealed significantly higher radiotracer uptake in both Apoe-/- and Ldlr-/- mice treated with anti-PD1 compared with the control groups. The increased expression of CCR2+ cells in Apoe-/- and Ldlr-/- mice was confirmed by immunostaining and flow cytometry. Single-cell RNA sequencing revealed elevated expression of CCR2 in myeloid cells. Mechanistically, IFNγ (interferon gamma) was essential for aggravated inflammation and atherosclerotic plaque progression following anti-PD1 treatment. Accelerated atherosclerotic plaque inflammation triggered by anti-PD1 treatment can be noninvasively detected by 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-ECL1i PET. Aggravated plaque inflammation is time- and dose-dependent and predominately mediated by IFNγ signaling. This study warrants further investigation of CCR2 PET as a noninvasive approach to visualize atherosclerotic plaque inflammation and explore the underlying mechanism following ICI treatment.

Somatostatin Receptor Type 2 as a Potential Marker of Local Myocardial Inflammation in Myocardial Infarction: Morphologic Data on Distribution in Infarcted and Normal Human Myocardium.

Nuclear imaging modalities can detect somatostatin receptor type 2 (SSTR2) in vivo as a potential marker of local post-MI inflammation. SSTR2+ macrophages are thought to be the main substrate for SSTR-targeted radioimaging. However, the distribution of SSTR2+ cells in the MI patients' myocardium is unknown. Using immunohistochemistry, we investigated the distribution of SSTR2+ cells in the myocardium of patients who died during the MI inflammatory phase (n = 7) compared to the control group of individuals with fatal trauma (n = 3). Inflammatory cellular landscapes evolve in a wave front-like pattern, so we divided the myocardium into histological zones: the infarct core (IC), the border zone (BZ), the remote zone (RZ), and the peri-scar zone (PSZ). The number of SSTR2+ neutrophils (NPs), SSTR2+ monocytes/macrophages (Mos/MPs), and SSTR2+ vessels were counted. In the myocardium of the control group, SSTR2+ NPs and SSTR2+ Mos/MPs were occasional, SSTR2+ vessels were absent. In the RZ, the picture was similar to the control group, but there was a lower number of SSTR2+ Mos/MPs in the RZ. In the PSZ, SSTR2+ vessel numbers were highest in the myocardium. In the IC, the median number of SSTR2+ NPs was 200 times higher compared to the RZ or control group myocardium, which may explain the selective uptake of SSTR-targeted radiotracers in the MI area during the inflammatory phase of MI.

Histopathological Correlation of Robotic-Assisted Radical Prostatectomy Specimen with Simultaneous 68GA-PSMA PET/MRI Findings in Cases of Adenocarcinoma Prostate

Background and Aims: 68Ga-PSMA PET represents a reasonable biomarker for presence of cancer of prostate (CaP). 68Ga-PSMA PET combined with simultaneous ‘multiparametric MRI’ (mpMRI) has the potential to be used for the detection and localisation of primary prostate cancer. It is therefore essential to correlate the histopathological findings of robotic-assisted radical prostatectomy (RARP) specimens with pre-operative PSMA PET/MRI. In addition, imaging with PSMA could be useful in estimating the aggressiveness of CaP. The current study aims at the correlation of histopathologic findings of RARP specimens with pre-operative combined 68Ga-PSMA PET/MRI imaging. Materials and Methods: Specimens retrieved after RARP in 38 patients of localised CaP were synchronised with pre-operative images obtained with simultaneous 68Ga-PSMA PET/MRI. Maximum scores of individual parameters such as PI-RADS, Gleason’s score and PSMA uptake (in SUV) were taken for each sector and used for statistical analysis. Results: The positive predictive value (PPV) and negative predictive value (NPV) of simultaneous 68Ga-PSMA PET and MRI in detecting malignancy were found to be 84.23% (95% CI: 80.74%–87.18%) and 63.92% (95% CI: 57.77%–69.65%), respectively. Combining 68Ga-PSMA PET and mpMRI improves the sensitivity to 81.48% (95% CI: 76.70%–85.67%), but the specificity was found to be 68.24% (95% CI: 60.09%–75.64%). It was found that SUV max correlated with the severity of GS ( P value &lt; .001). Conclusion: Prediction and localisation of histological malignancy in the prostate could be improved pre-operatively by adding 68Ga-PSMA PET to mpMRI imaging. The SUV of abnormal uptake of 68Ga-PSMA radiotracer is predictive of aggressiveness of tumour as reflected in the Gleason score.

68Ga]Ga-RAYZ-8009: A Glypican-3-Targeted Diagnostic Radiopharmaceutical for Hepatocellular Carcinoma Molecular Imaging-A First-in-Human Case Series.

To date, the imaging and diagnosis of hepatocellular carcinoma (HCC) rely on CT/MRI, which have well-known limitations. Glypican-3 (GPC3) is a cell surface receptor highly expressed by HCC but not by normal or cirrhotic liver tissue. Here we report initial clinical results of GPC3-targeted PET imaging with [68Ga]Ga-DOTA-RYZ-GPC3 (RAYZ-8009), a peptide-based GPC3 ligand in patients with known or suspected HCC. Methods: [68Ga]Ga-RAYZ-8009 was obtained after labeling the peptide precursor with 68Ga from a 68Ge/68Ga generator and heating at 90°C for 10 min followed by sterile filtration. After administration of [68Ga]Ga-RAYZ-8009, a dynamic or static PET/CT scan was acquired between 45 min and 4 h after administration. Radiotracer uptake was measured by SUVs for the following tissues: suspected or actual HCC or hepatoblastoma lesions, non-tumor-bearing liver, renal cortex, blood pool in the left ventricle, and gastric fundus. Additionally, tumor-to-healthy-liver ratios (TLRs) were calculated. Results: Twenty-four patients (5 patients in the dynamic protocol; 19 patients in the static protocol) were scanned. No adverse events occurred. Two patients had no lesion detected and did not have HCC during follow-up. In total, 50 lesions were detected and analyzed. The mean SUVmax of these lesions was 19.6 (range, 2.7-95.3), and the mean SUVmean was 10.1 (range, 1.0-49.2) at approximately 60 min after administration. Uptake in non-tumor-bearing liver and blood pool rapidly decreased over time and became negligible 45 min after administration (mean SUVmean, <1.6), with a continuous decline to 4 h after administration (mean SUVmean, 1.0). The opposite was observed for HCC lesions, for which SUVs and TLRs continuously increased for up to 4 h after administration. In individual lesion analysis, TLR was the highest between 60 and 120 min after administration. Uptake in the gastric fundus gradually increased for up to 45 min (to an SUVmax of 31.3) and decreased gradually afterward. Conclusion: [68Ga]Ga-RAYZ-8009 is safe and allows for high-contrast imaging of GPC3-positive HCC, with rapid clearance from most normal organs. Thereby, [68Ga]Ga-RAYZ-8009 is promising for HCC diagnosis and staging. Further research is warranted.

Role of [18F]FAPI-04 in staging and therapeutic management of intrahepatic cholangiocarcinoma: prospective comparison with [18F]FDG PET/CT

BackgroundFluorine-18 fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) has some limitations in diagnosis of Intrahepatic cholangiocarcinoma (ICC).Materials and methodsPatients with histologically confirmed ICC who underwent both [18F]FDG and 18F-labeled fibroblast-activation protein inhibitors ([18F]FAPI)-04 PET/CT were prospectively analyzed. The maximum standard uptake value (SUVmax), tumor-to-background ratio (TBR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), [18F]FAPI–avid tumor volume (FTV), total lesion fibroblast activation protein expression (TLF) were compared between the two modalities by paired Wilcoxon signed-rank test and Mann–Whitney U test, and McNemar’s test was used to assess the diagnostic accuracy between the two techniques.ResultsIn total, 23 patients with 389 lesions were included. Compared to [18F]FDG, [18F]F-FAPI-04 PET/CT demonstrated a higher detection rate for intrahepatic lesions (86.3% vs. 78.2% P = 0.040), lymph node metastases (85.2% vs. 68.2%, P = 0.007), peritoneal metastases (100% vs. 93.8%), and bone metastases (100% vs. 70.5%, P < 0.001). [18F]FAPI-04 PET showed higher SUVmax, TBR and greater tumor burden values than [18F]FDG PET in non-cholangitis intrahepatic lesions (SUVmax: 8.7 vs. 6.4, P < 0.001; TBR: 8.0 vs. 3.5, P < 0.001; FTV vs. MTV: 41.3 vs. 12.4, P < 0.001; TLF vs. TLG: 223.5 vs. 57.0, P < 0.001), lymph node metastases (SUVmax: 6.5 vs. 5.5, P = 0.042; TBR: 5.4 vs. 3.9, P < 0.001; FTV vs. MTV: 2.0 vs. 1.5, P = 0.026; TLF vs. TLG: 9.0 vs. 7.8 P = 0.024), and bone metastases (SUVmax: 9.7 vs. 5.25, P < 0.001; TBR: 10.8 vs. 3.0, P < 0.001; TLF vs. TLG: 9.8 vs. 4.2, P < 0.001). However, [18F]FDG showed higher radiotracer uptake (SUVmax: 14.7 vs. 8.4, P < 0.001; TBR: 7.4 vs. 2.8, P < 0.001) than [18F]FAPI-04 PET/CT for 6 patients with obstructive cholangitis. [18F]FAPI-04 PET/CT yielded a change in planned therapy in 6 of 23 (26.1%) patients compared with [18F]FDG.Conclusions[18F]FAPI-04 PET/CT had higher detection rate and radiotracer uptake than [18F]FDG PET/CT in intrahepatic lesions, lymph node metastases, and distant metastases, especially in bone. Therefore, [18F]FAPI-04 PET/CT may be a promising technique for diagnosis and staging of ICC.Trial registrationClinical Trials, NCT05485792. Registered 1 August 2022, retrospectively registered, https//clinicaltrials.gov/study/NCT05485792?cond=NCT05485792&rank=1.