The inferior performance of [68Ga]Ga-FAPI-04 PET/CT as a diagnostic and theranostic biomarker in [177Lu]Lu-DOTATATE refractory well-differentiated neuroendocrine tumors.

PURPOSE: We aimed to investigate the potential of [68Ga]Ga-FAPI-04 PET/CT as an alternative diagnostic and theranostic tool in well-differentiated NETs refractory to [177Lu]Lu-DOTATATE therapy. METHODS: Patients who received at least two cycles of [177Lu]Lu-DOTATATE therapy for metastatic NETs and progressed under treatment were included. All patients had performed [68Ga]Ga-DOTATATE and [68Ga]Ga-FAPI-04 PET/CT within 3 weeks. The number of PET-positive lesions related to NETs and tumor sites was documented. Mann-Whitney U and chi-square tests were used to compare SUVmax levels of tracers and the number of detected metastases. RESULTS: Twelve patients (7 male, 5 female) who met the eligibility criteria were included in the study. Ten patients had grade 1-2 NET of various origins, and two had paraganglioma and pheochromocytoma. One hundred ninety-eight of 230 lesions (86%) were SSTR positive with a median SUVmax of 16.6 (2.2-76.5), and 88 of 230 lesions (38.2%) were [68Ga]Ga-FAPI-04 positive with a median SUVmax of 5.1 (2.3-21). Median SUVmax level and detected number of tumors were significantly higher in [68Ga]Ga-DOTATATE PET/CT (p=<0.001). [68Ga]Ga-FAPI-04 PET/CT was completely (n:2) or almost completely (n:3) negative in 5 (42%) patients. Two (17%) patients had flip-flop SSTR/FAPI uptake in tumors. In four patients (33%), tumor uptake or the number of PET-positive lesions was inferior in [68Ga]Ga-FAPI-04 PET/CT. In only one patient (8%), tumor uptakes were higher in [68Ga]Ga-FAPI-04 PET/CT. Low-dose [177Lu]Lu-FAPI-46 dosimetry was performed on the FAPI-dominant patient; absorbed radiation doses per GBq were 1.26 Gy, 0.36 Gy, 0.32 Gy, and 0.2 Gy for kidneys, liver, spleen, and total body, respectively. The mean absorbed dose per GBq was 0.33 Gy for liver mass and 0.41 Gy for metastatic lymph nodes. CONCLUSION: Our preliminary results demonstrated that [68Ga]Ga-FAPI-04 PET/CT mainly failed in well-differentiated NETs refractory to [177Lu]Lu-DOTATATE therapy and had a limited role as an alternative diagnostic or theranostic agent. Further investigations with a larger patient population are required to determine the impact of [68Ga]Ga-FAPI-04 PET/CT on NETs.

Reduced uptake pattern on 68 Ga-DOTATATE-scan may indicate necrosis predicting aggressive behavior in pheochromocytoma and paragangliomas (PPGLs).

BACKGROUND: Predicting malignancy among pheochromocytoma paragangliomas (PPGLs) remains a challenge, with only limited understanding of the clinical and molecular characteristics. It has been suggested that reduced avidity of a PPGL on 68 Ga-DOTATATE PET/CT could be a sign of not only altered metabolic activity, but also of increased biologic aggressiveness, possibly due to loss of SSTR-expression. DESIGN: Retrospective cohort review. PATIENTS AND MEASUREMENTS: Thirty-seven patients who underwent treatment for PPGL at a tertiary institution over the period 2010-2022, had their biochemical, radiological, and clinicopathological variables collected. RESULTS: Five of 37 (13%) patients (5 males) with a mean age of 42 years were found to have malignant PPGLs. The mean size of the tumors were 5.4 cm, with 4 located in the paraaortic area and 1 in right adrenal. Functional imaging with 68 Ga-DOTATATE PET/CT showed a mean SUVmax of 4.5. Four of 5 patients underwent open resection of the tumors under general anesthesia following preoperative alpha blockade with oral phenoxybenzamine. The mean PASS score of the excised tumors was 5.5 in keeping with biologically aggressive tumors, with evidence of necrosis. All but 1 patient had germline SDHB-mutation (Deletion Exon 1). Postintervention after a mean follow-up of 31 months, 2 of 5 (40%) patient developed spinal metastasis and 1 patients (25%) died of cardiac complications. CONCLUSION: A non-highly avid PPGL on DOTATE scan should be considered as possibly having necrosis of tumors indicating a more aggressive tumor-biology. There might be a subgroup of patients in whom FDG-PET scan should be considered to gain additional information.

Potential clinical utility of 68Ga-DOTATATE PET/CT for detection and response assessment in cardiac sarcoidosis.

BACKGROUND: Somatostatin receptor is expressed in sarcoid granulomas, and preliminary clinical studies have shown that myocardial sarcoidosis can be identified on somatostatin receptor-targeted PET. We examined the potential clinical use of 68Ga-DOTATATE PET/CT for diagnosis and response assessment in cardiac sarcoidosis compared to 18F-FDG PET/CT. METHODS: Eleven cardiac sarcoidosis patients with 18F-FDG PET/CT were prospectively enrolled for cardiac 68Ga-DOTATATE PET/CT. The two PET/CT studies were interpreted independently and were compared for patient-level and segment-level concordance, as well as for the degree of radiotracer uptake. Follow-up 68Ga-DOTATATE PET/CT was performed in eight patients. RESULTS: Patient-level concordance was 91%: ten patients had multifocal DOTATATE uptake (active cardiac sarcoidosis) and one patient showed diffuse DOTATATE uptake. Segment-level agreement was 77.1% (Kappa 0.53 ± 0.07). The SUVmax-to-blood pool ratio was lower on 68Ga-DOTATATE PET/CT (3.2 ± 0.6 vs. 4.9 ± 1.5, P = 0.006 on paired t test). Follow-up 68Ga-DOTATATE PET/CT showed one case of complete response and one case of partial response, while 18F-FDG PET/CT showed four cases of response, including three with complete response. CONCLUSION: Compared to 18F-FDG PET/CT, 68Ga-DOTATATE PET/CT can identify active cardiac sarcoidosis with high patient-level concordance, but with moderate segment-level concordance, low signal-to-background ratio, and underestimation of treatment response.

68 Ga-DOTATATE PET/CT imaging in endogenous hyperinsulinemic hypoglycemia: A tertiary endocrine centre experience.

OBJECTIVE: Literature regarding utility of 68 Ga-DOTATATE PET/CT in insulinoma localization across various subgroups [benign/malignant/multiple endocrine neoplasia-1 (MEN-1) syndrome associated] remains scarce. In this study, the performance of 68 Ga-DOTATATE PET/CT was compared with contrast-enhanced computed tomography (CECT) and 68 Ga-NODAGA-Exendin-4 PET/CT (whenever available) in an endogenous hyperinsulinemic hypoglycemia (EHH) cohort. DESIGN: Retrospective audit. PATIENTS: EHH patients [N = 36, lesions (n) = 49, final diagnosis: benign sporadic insulinoma (BSI) (N = 20), malignant insulinoma (N = 4, n = 14), MEN-1 syndrome associated insulinoma (N = 9, n = 15), Munchausen syndrome (N = 2) and drug-induced hypoglycemia (N = 1)] having both preoperative imaging modalities (CECT and 68 Ga-DOTATATE PET/CT). MEASUREMENTS: Per-lesion sensitivity (Sn) and positive predictive value (PPV) for histopathological diagnosis of insulinoma. RESULTS: Sn and PPV of 68 Ga-DOTATATE PET/CT were 67.3% and 89.2%; 55% and 100%; 85.7% and 100%; and 66.7% and 77% for overall EHH, BSI, malignant, and MEN-1 syndrome associated insulinoma cohorts respectively. Despite having comparatively lower sensitivity in BSI cohort, 68 Ga-DOTATATE PET/CT localized a pancreatic tail lesion missed by other modalities. 68 Ga-DOTATATE PET/CT had comparatively higher sensitivity in malignant insulinoma than BSI cohort. 68 Ga-DOTATATE PET/CT also paved the way for successful response to 177 Lu-based peptide receptor radionuclide therapy (PRRT). In MEN-1 cases, lower PPV as compared with BSI was due to uptake in non-insulinoma pancreatic neuroendocrine tumours (Pan-NET). CONCLUSIONS: 68 Ga-DOTATATE PET/CT has supplemental role in selected cases of BSI with negative and/or discordant results with CECT and 68 Ga-NODAGA-Exendin-4 PET/CT. In malignant insulinoma, 68 Ga-DOTATATE-PET/CT has an additional theranostic potential. Interference due to uptake in non-insulinoma Pan-NET in MEN-1 syndrome may hinder insulinoma localization with 68 Ga-DOTATATE-PET/CT.

A prospective head-to-head comparison of 68 Ga-NOTA-3P-TATE-RGD and 68 Ga-DOTATATE in patients with gastroenteropancreatic neuroendocrine tumours.

PURPOSE: The aim of this study was to compare 68 Ga-NOTA-3P-TATE-RGD, a dual somatostatin receptor 2- and integrin αVß3-targeting tracer, to 68 Ga-DOTATATE in a single group of patients with gastroenteropancreatic (GEP)-neuroendocrine tumours (NETs). METHODS: Thirty-five patients with histologically confirmed GEP-NETs (5 grade 1, 28 grade 2, and 2 grade 3 tumours) were prospectively enrolled with informed consent. The primary tumour mainly originated from the pancreas and rectum. All patients were scanned with both 68 Ga-NOTA-3P-TATE-RGD PET/CT and 68 Ga-DOTATATE PET/CT within a week and compared on a head-to-head basis. Sixteen patients also had conventional 18F-FDG PET/CT. Images were evaluated semi-quantitatively using maximum standardized uptake values (SUVmax) of tumour and tumour-to-background ratio. RESULTS: All patients had at least one positive lesion on each of the two scans. A total of 1190 and 1106 lesions were detected on 68 Ga-NOTA-3P-TATE-RGD images and 68 Ga-DOTATATE images, respectively (P = 0.152). 68 Ga-NOTA-3P-TATE-RGD PET/CT revealed significantly more lesions in the liver than 68 Ga-DOTATATE PET/CT (634 vs. 532, P = 0.021). Both tracers produced comparable results for detecting primary tumours (20 vs. 20, P = 1.000), lymph node metastases (101 vs. 102, P = 0.655), and bone metastases (381 vs. 398, P = 0.244). The tumour SUVmax in 12 patients was significantly higher for 68 Ga-NOTA-3P-TATE-RGD than for 68 Ga-DOTATATE (27.2 ± 13.6 vs. 19.5 ± 10.0, P < 0.001); among them, 9 had 18F-FDG PET/CT and all were found to be FDG-positive. The remaining 23 patients had significantly higher 68 Ga-DOTATATE uptake than 68 Ga-NOTA-3P-TATE-RGD uptake (22.3 ± 16.4 vs. 11.9 ± 7.5, P < 0.001); among them, 7 had 18F-FDG PET/CT and 6 were FDG-negative. Generally, 68 Ga-DOTATATE demonstrated higher tumour SUVmax than 68 Ga-NOTA-3P-TATE-RGD (20.8 ± 16.0 vs. 14.2 ± 8.9, P < 0.001), including primary tumours, liver lesions, lymph node lesions, and bone lesions. However, the tumour-to-background ratio of liver lesions was significantly higher when using 68 Ga-NOTA-3P-TATE-RGD compared with that when using 68 Ga-DOTATATE (8.4 ± 5.5 vs. 4.7 ± 3.7, P < 0.001). CONCLUSION: 68 Ga-NOTA-3P-TATE-RGD performed better than 68 Ga-DOTATATE in detection of liver metastases with a higher tumour-to-background ratio. Moreover, 68 Ga-NOTA-3P-TATE-RGD tended to demonstrate higher uptake over 68 Ga-DOTATATE in FDG-avid NETs. TRIAL REGISTRATION: Dual SSTR2 and Integrin αvß3 Targeting PET/CT Imaging (NCT02817945, registered 5 November 2018). URL OF REGISTRY: https://clinicaltrials.gov/ct2/show/NCT02817945.

A prospective randomized, double-blind study to evaluate the diagnostic efficacy of 68Ga-NODAGA-LM3 and 68Ga-DOTA-LM3 in patients with well-differentiated neuroendocrine tumors: compared with 68Ga-DOTATATE.

PURPOSE: The purpose of this study is to evaluate the diagnostic efficacy of 68 Ga-NODAGA-LM3 and 68 Ga-DOTA-LM3 and compare them with 68 Ga-DOTATATE in patients with well-differentiated neuroendocrine tumors. METHODS: Patients were prospectively recruited and equally randomized into two arms: Arm A, patients would undergo a whole-body 68 Ga-NODAGA-LM3 PET/CT scan on the 1st day and 68 Ga-DOTATATE PET/CT scan on the 2nd day; Arm B, patients would undergo a whole-body 68 Ga-DOTA-LM3 PET/CT scan on the 1st day and 68 Ga-DOTATATE PET/CT scan on the 2nd day. Biodistribution in normal organs, lesion detection ability, and tumor uptake were compared between antagonist and agonist in each arm. RESULTS: A total of 40 patients with well-differentiated NETs, 20 in each arm, were recruited in the study. 68 Ga-NODAGA-LM3 showed a similar pattern as 68 Ga-DOTATATE, while 68 Ga-DOTA-LM3 demonstrated significantly lower uptake in almost all normal organs compared to 68 Ga-DOTATATE. Both 68 Ga-NODAGA-LM3 and 68 Ga-DOTA-LM3 showed superiority in lesion detection compared to 68 Ga-DOTATATE on lesion-based and patient-based comparison. 68 Ga-NODAGA-LM3 showed a significantly higher tumor uptake (median SUVmax 29.1 versus 21.6, P < 0.05) and tumor-to-background ratio (median tumor-to-liver ratio 5.0 versus 2.9, P < 0.05) compared to 68 Ga-DOTATATE. 68 Ga-DOTA-LM3 showed comparable uptake (median SUVmax 16.1 versus 17.8, P = 0.714) and higher tumor-to-background ratio (median tumor-to-liver ratio 5.2 versus 2.1, P < 0.05). CONCLUSION: Both 68 Ga-NODAGA-LM3 and 68 Ga-DOTA-LM3 are promising SSTR2 antagonists for neuroendocrine tumors. They demonstrated superiority in diagnostic efficacy compared to agonist 68 Ga-DOTATATE. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT04318561.

Correlation and Comparison of Somatostatin Receptor Type 2 Immunohistochemical Scoring Systems with 68Ga-DOTATATE Positron Emission Tomography/Computed Tomography Imaging in Gastroenteropancreatic Neuroendocrine Neoplasms.

INTRODUCTION: The overexpression of somatostatin receptor type 2 (SSTR2) is a unique characteristic of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs), which establishes the basis for both diagnosis and therapy. The SSTR status can be evaluated by immunohistochemical staining (IHC) and 68Ga-DOTATATE positron emission tomography/computed tomography (PET/CT) imaging. This study attempted to determine the relationship between IHC and 68Ga-DOTATATE PET/CT imaging and to explore the optimal cutoff value for SSTR IHC reading. PATIENTS AND METHODS: A total of 100 GEP-NENs with SSTR PET/CT and pathological data were retrospectively analyzed, which consisted of neuroendocrine tumor (NET) G1 (n = 9), NET G2 (n = 64), NET G3 (n = 13), neuroendocrine carcinoma ( n = 10), and mixed neuroendocrine-non-NENs ( n = 4). SSTR2-IHC results were interpreted by 4 well-established semiquantitative scoring systems, including human epidermal growth factor receptor 2 (HER2) score, Volante score, H score, and immunoreactive score. RESULTS: In the homogeneous SSTR2 expression group (accounting for 57% of all cases), the 4 scoring systems were highly concordant with each other (Kendall's Tau-b coefficient range: 0.80-0.96, p < 0.001) and also highly correlated with the 68Ga-DOTATATE PET/CT imaging results (Spearman's rank correlation coefficients: 0.71, 0.86, 0.80, and 0.71, p < 0.001). In the heterogeneous group (43%), the 4 scoring systems revealed a lower level of concordance (the Kendall Tau-b coefficient range: 0.40-0.75, p < 0.01), and the correlation with 68Ga-DOTATATE PET/CT imaging was also lower, albeit statistically significant (Spearman's rank correlation coefficients: 0.53, 0.38, 0.36, and 0.33, p < 0.05). Heterogeneous SSTR2 expression was mainly observed in the HER2 2+ cases, for which the combination with H score could help identify positive cases with increased sensitivity and specificity. The highest sensitivity and specificity of H scores in predicting the imaging results were achieved at 86.10 and 89.30% when defining the cutoff value as 160, indicating that 80% of the tumor cells were moderately positive or 55% were strongly positive. CONCLUSIONS: SSTR2 IHC was found to predict 68Ga-DOTATATE PET/CT imaging accurately, especially in the homogeneous expression group. According to the positive 68Ga-DOTATATE PET/CT outcomes, 80% of the tumor cells moderately positive or 55% strongly positive was the cutoff values for SSTR2-IHC reading.

The Triple-Tracer strategy against Metastatic PrOstate cancer (3TMPO) study protocol.

OBJECTIVE: To determine the prevalence of intra-patient inter-metastatic heterogeneity based on positron emission tomography (PET)/computed tomography (CT) in patients with metastatic castration-resistant prostate cancer (mCRPC) and to determine the prevalence of neuroendocrine disease in these patients and their eligibility for radioligand therapies (RLTs). PATIENTS AND METHODS: This multicentre observational prospective clinical study will include 100 patients with mCRPC from five Canadian academic centres. Patients with radiological or biochemical progression and harbouring at least three metastases by conventional imaging will be accrued. Intra-patient inter-metastatic heterogeneity will be determined with triple-tracer imaging using fluorine-18 fluorodeoxyglucose (18 F-FDG), gallium-68-(68 Ga)-prostate-specific membrane antigen (PSMA)-617 and 68 Ga-DOTATATE, which are a glucose analogue, a PSMA receptor ligand and a somatostatin receptor ligand, respectively. The 68 Ga-PSMA-617 and 18 F-FDG PET/CT scans will be performed first. If at least one PSMA-negative/FDG-positive lesion is observed, an additional PET/CT scan with 68 Ga-DOTATATE will be performed. The tracer uptake of individual lesions will be assessed for each PET tracer and patients with lesions presenting discordant uptake profiles will be considered as having inter-metastatic heterogeneous disease and may be offered a biopsy. EXPECTED RESULTS: The proposed triple-tracer approach will allow whole-body mCRPC characterisation, investigating the inter-metastatic heterogeneity in order to better understand the phenotypic plasticity of prostate cancer, including the neuroendocrine transdifferentiation that occurs during mCRPC progression. Based on 68 Ga-PSMA-617 or 68 Ga-DOTATATE PET positivity, the potential eligibility of patients for PSMA and DOTATATE-based RLT will be assessed. Non-invasive whole-body determination of mCRPC heterogeneity and transdifferentiation is highly innovative and might establish the basis for new therapeutic strategies. Comparison of molecular imaging findings with biopsies will also link metastasis biology to radiomic features. CONCLUSION: This study will add novel, biologically relevant dimensions to molecular imaging: the non-invasive detection of inter-metastatic heterogeneity and transdifferentiation to neuroendocrine prostate cancer by using a multi-tracer PET/CT strategy to further personalise the care of patients with mCRPC.

68 Ga-DOTATATE PET and functional imaging in pediatric pheochromocytoma and paraganglioma.

Pheochromocytoma and paraganglioma (PPGL) are rare neuroendocrine tumors in childhood. Up to 40% of PPGL are currently thought to be associated with a hereditary predisposition. Nuclear medicine imaging modalities such as fluorodeoxyglucose positron emission tomography (18 F-FDG PET), 68 Ga-DOTATATE PET, and 123 I-metaiodobenzylguanidine (123 I-MIBG) scintigraphy play an essential role in the staging, response assessment, and determination of suitability for targeted radiotherapy in patients with PPGL. Each of these functional imaging modalities targets a different cellular characteristic and as such can be complementary to anatomic imaging and to each other. With the recent US Food and Drug Administration approval and increasing use of 68 Ga-DOTATATE for imaging in children, the purpose of this article is to use a case-based approach to highlight both the advantages and limitations of DOTATATE imaging as it is compared to current radiologic imaging techniques in the staging and response assessment of pediatric PPGL, as well as other neuroendocrine malignancies.

Sporadic Primary Pheochromocytoma: A Prospective Intraindividual Comparison of Six Imaging Tests (CT, MRI, and PET/CT Using 68Ga-DOTATATE, FDG, 18F-FDOPA, and 18F-FDA).

BACKGROUND. Recent professional society guidelines for radionuclide imaging of sporadic pheochromocytoma (PHEO) recommend 18F-fluorodihydroxyphenylala-nine (18F-FDOPA) as the radiotracer of choice, deeming 68Ga-DOTATATE and FDG to be second- and third-line agents, respectively. An additional agent, 18F-fluorodopamine (18F-FDA), remains experimental for PHEO detection. A paucity of research has performed head-to-head comparison among these agents. OBJECTIVE. The purpose of this study was to perform an intraindividual comparison of 68Ga-DOTATATE PET/CT, FDG PET/CT, 18F-FDOPA PET/CT, 18F-FDA PET/CT, CT, and MRI in visualization of sporadic primary PHEO. METHODS. This prospective study enrolled patients referred with clinical suspicion for sporadic PHEO. Patients were scheduled for 68Ga-DOTATATE PET/CT, FDG PET/CT, 18F-FDOPA PET/CT, 18F-FDA PET/CT, whole-body staging CT (portal venous phase), and MRI within a 3-month period. PET/CT examinations were reviewed by two nuclear medicine physicians, and CT and MRI were reviewed by two radiologists; differences were resolved by consensus. Readers scored lesions in terms of confidence in diagnosis of PHEO (1-5 scale; 4-5 considered positive for PHEO). Lesion-to-liver SUVmax was computed using both readers' measurements. Interreader agreement was assessed using intraclass correlation coefficients (ICCs) for SUVmax. Analysis included only patients with histologically confirmed PHEO on resection. RESULTS. The analysis included 14 patients (eight women, six men; mean age, 52.4 ± 16.8 [SD] years) with PHEO. Both 68Ga-DOTATATE PET/CT and FDG PET/CT were completed in all 14 patients, 18F-FDOPA PET/CT in 11, 18F-FDA PET/CT in 7, CT in 12, and MRI in 12. Mean conspicuity score for PHEO was 5.0 ± 0.0 for 18F-FDOPA PET/CT, 4.7 ± 0.5 for MRI, 4.6 ± 0.8 for 18F-FDA PET/CT, 4.4 ± 1.0 for 68Ga-DOTATATE PET/CT, 4.3 ± 1.0 for CT, and 4.1 ± 1.5 for FDG PET/CT. The positivity rate for PHEO was 100.0% (11/11) for 18F-FDOPA PET/CT, 100.0% (12/12) for MRI, 85.7% (6/7) for 18F-FDA PET/CT, 78.6% (11/14) for FDG PET/CT, 78.6% (11/14) for 68Ga-DOTATATE PET/CT, and 66.7% (8/12) for CT. Lesion-to-liver SUVmax was 10.5 for 18F-FDOPA versus 3.0-4.2 for the other tracers. Interreader agreement across modalities ranged from 85.7% to 100.0% for lesion positivity with ICCs of 0.55-1.00 for SUVmax measurements. CONCLUSION. Findings from this small intraindividual comparative study support 18F-FDOPA PET/CT as a preferred first-line imaging modality in evaluation of sporadic PHEO. CLINICAL IMPACT. This study provides data supporting current guidelines for imaging evaluation of suspected PHEO. TRIAL REGISTRATION. ClinicalTrials.gov NCT00004847.

Tumor-induced osteomalacia characterized by "painful knee joint with difficulty in moving": a case report.

BACKGROUND: Tumor-related osteomalacia (TIO) is a rare paraneoplastic syndrome characterized by severe hypophosphatemia and osteomalacia. The diagnosis of TIO can be very difficult because of its nonspecific nature of clinical manifestations. Here we reported a case of young TIO patient with "painful knee joint with difficulty in moving" to improve the clinical diagnosis and treatment levels. CASE PRESENTATION: The patient's clinical features were consistent with TIO. A tumor was successfully located in left tibial by 68Ga-DOTATATE PET/CT, and then was surgically resected. Upon pathologic assessment, the tumor was diagnosed as phosphaturia stromal tumor (PMT) with positive Vim staining. After the surgery, serum phosphate level rapidly recovered and symptoms significantly improved. CONCLUSION: TIO should be considered in patients with chronically hypophosphorus osteomalacia in the setting of no family history. Early removal of the responsible tumors is clinically essential for the treatment, and imaging examination is of great significance for tumor localization.

Myocardial uptake of 68Ga-DOTATATE: correlation with cardiac disease and risk factors.

BACKGROUND: Myocardial uptake on 68Ga-DOTATATE PET/CT is often observed and its clinical relevance is poorly understood. PURPOSE: To detect any correlation between myocardial uptake of 68Ga-DOTATATE and presence of cardiac disease or risk factors. MATERIAL AND METHODS: In this institutional review board-approved retrospective study, we reviewed 68Ga-DOTATATE PET/CT scans in our institution between 1 May 2018 and 30 September 2018. A semi-quantitative score (MUS) for myocardial uptake of 68Ga-DOTATATE was developed by measuring mean standardized uptake value (SUV) in five myocardial regions, corrected by blood pool activity, and MUS was validated between two readers. We investigated the relationship between MUS and presence of cardiac disease or risk factors, including Framingham score and coronary calcification. RESULTS: A total of 145 scans were included (79 women; mean age = 56.9 ± 13.7 years). Inter-reader agreement was excellent with intraclass correlation coefficient (r) = 0.964 (95% confidence interval [CI] = 0.903-0.987; P < 0.001). There was a weak but significant positive correlation between MUS and presence of coronary calcifications (Spearman rho = 0.20; P = 0.016). MUS was higher in patients with heart disease or risk factors (n = 83, mean MUS 2.03, 95% CI = 1.85-2.21) compared to those without (n = 23, mean MUS 1.40, 95% CI = 1.17-1.62; P < 0.001), although the cardiac disease group was older with a higher percentage of men (62.0 years, 57.8% men compared to 47.6 years, 13.0% men; P value <0.0001 for both comparisons). CONCLUSION: For patients undergoing 68Ga-DOTATATE PET/CT scan, an elevated MUS might indicate an underlying heart disease.

Cardiac hemangioma mimicking a neuroendocrine tumor on 68 Ga Dotatate PET/CT.

Cardiac hemangioma is a rare, benign primary tumor characterized by endothelial proliferation. While reports of cardiac hemangiomas demonstrating 18 F FDG avidity and other forms of hemangiomas showing 68 Ga Dotatate avidity have been published, we present a rare case of primary cardiac hemangioma demonstrating 68 Ga Dotatate avidity, mimicking a primary neuroendocrine tumor.

68 Ga-DOTATATE Positron Emission Tomography-Computed Tomography Quantification Predicts Response to Somatostatin Analog Therapy in Gastroenteropancreatic Neuroendocrine Tumors.

BACKGROUND: Somatostatin analogs (SSAs) are the frontline antitumor therapy in advanced well-differentiated gastroenteropancreatic neuroendocrine tumors (GEP-NETs). A subset of patients demonstrate early disease progression on SSA therapy, yet the currently known predictors for treatment failure lack specificity to affect therapeutic decision. SSAs target tumor somatostatin receptors, the level of which can be quantitatively assessed with 68 Ga-DOTATATE positron emission tomography-computed tomography (PET/CT). We investigated the ability of 68 Ga-DOTATATE PET/CT to predict response to SSA therapy. MATERIALS AND METHODS: The records of 108 consecutive patients with well-differentiated grade 1-2 GEP-NETs on SSA monotherapy who received 68 Ga-DOTATATE PET/CT scans were retrospectively reviewed to obtain baseline characteristics, 68 Ga-DOTATATE maximum standardized uptake value (SUVmax), and progression-free survival (PFS) data. The optimal SUVmax cutoff for patient stratification was obtained with receiver operating characteristic curve analysis. PFS in the high versus low SUVmax groups was compared with Kaplan-Meier survival analysis. The effects of baseline characteristics and SUVmax on PFS were examined with univariate and multivariate Cox regression. RESULTS: 68 Ga-DOTATATE SUVmax predicted therapeutic failure with sensitivity and specificity of 39% and 98%, respectively. SUVmax of <18.35 was associated with shorter PFS, which was reproduced in the subgroup analysis of SSA-naïve patients. Low SUVmax was the only predictor of early treatment failure (hazard ratio, 6.85) in multivariate analysis, as well as in the subgroup analysis of grade 2 GEP-NETs. CONCLUSION: Low SUVmax on 68 Ga-DOTATATE PET/CT independently predicts early failure on SSA monotherapy in patients with well-differentiated grade 1-2 GEP-NET. Patients with lack of expected benefit from SSA therapy can be readily identified using routine 68 Ga-DOTATATE PET/CT with very high specificity. IMPLICATIONS FOR PRACTICE: Based on 68 Ga-DOTATATE positron emission tomography-computed tomography imaging, clinicians can better inform patients on the expected benefit of somatostatin analog therapy for gastroenteropancreatic neuroendocrine tumors, especially when access to the therapy is difficult, and offer proactive discussion on alternative management options.

Theranostic implications of molecular imaging phenotype of well-differentiated pulmonary carcinoid based on 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT.

PURPOSE: This study aimed to analyse the molecular imaging (MI) phenotype of typical carcinoid (TC) and atypical carcinoid (AC) by 68Ga-DOTATATE (GaTATE) and 18F-FDG (FDG) PET/CT with the emphasis on its potential theranostic implications for peptide receptor radionuclide therapy (PRRT). METHODS: Retrospective review of patients with biopsy-proven TC or AC undergoing both GaTATE and FDG PET/CT at presentation. Based on correlative CT or MRI, positive lesions on either scan were defined by uptake above liver parenchyma. Per patient MI phenotypic pattern was classified as score 1, if all lesions were negative on both scans; score 2, if all were GaTATE positive/FDG negative; score 3, if all lesions were GaTATE positive but some or all were also FDG positive and score 4, if there were any GaTATE negative/FDG positive lesions. Scores 1 and 4 were deemed unsuitable for PRRT. RESULTS: Of 56 patients (median age 66.5 years, 32 female), 22 had TC, and 34 had AC. Distant metastases were seen in 32% of TC and 94% of AC. At a median follow-up of 37 months for TC and 38 months for AC, 100% and 63% were alive, respectively. Median OS for AC was 56 months (95% CI 43, not reached [NR]), and TC was NR. On inter-patient dual-tracer analysis, scores 1, 2, 3 and 4 were 23%, 18%, 36% and 23% in TC and 3%, 15%, 32% and 50% in AC, respectively. In 16 patients (score 2, N = 3; score 3, N = 12; score 4, N = 1) who were treated with PRRT, disease control rate at 3 months and OS were, 85% and 54.6 months (95% CI 44-70), respectively. CONCLUSIONS: TC and AC showed a wide inter-patient phenotypic heterogeneity on GaTATE and FDG with around half of patients (46% TC and 53% AC) having an unsuitable phenotype for PRRT. Dual-tracer MI phenotype can be used to select the most suitable patients for PRRT.

Head-to-head comparison of 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT in localizing tumors with ectopic adrenocorticotropic hormone secretion: a prospective study.

PURPOSE: Localizing the source of ectopic adrenocorticotropic hormone secretion (EAS) is challenging. This study compared the diagnostic value of 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT in tumors with EAS. METHODS: Thirty-six patients with a suspicion of EAS were enrolled to undergo both 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT within 4 weeks for comparison. Twenty-three underwent surgical resection or biopsy. Immunohistochemical staining for SSTR2 and Ki-67 was performed to correlate with 68Ga-DOTATATE uptake and 18F-FDG uptake, respectively. RESULTS: EAS tumors were observed in 20/23 patients. Among the 20 patients with histologically proven EAS tumors, 68Ga-DOTATATE PET/CT correctly identified the tumor in 15 (75.0%), with an SUVmax ranging from 1.4 to 20.7 (6.7 ± 5.5). 18F-FDG PET/CT correctly identified the tumor in 12 (60.0%) patients, with an SUVmax ranging from 1.8 to 10.0 (4.0 ± 2.1). Moreover, 68Ga-DOTATATE PET/CT unmasked the sources of EAS in 6 patients with negative 18F-FDG uptake, and 18F-FDG PET/CT unmasked the sources in 3 patients with negative 68Ga-DOTATATE uptake, resulting in EAS tumors being identified in 18 (90%) patients by combining 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT. CONCLUSIONS: 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT are complementary in localizing and discriminating the source of EAS. 68Ga-DOTATATE PET/CT combined with 18F-FDG PET/CT had higher detection rate than each alone. TRIAL REGISTRATION: 68Ga-DOTATATE PET/CT in Neuroendocrine Tumors (NCT04041882) URL OF REGISTRY: https://clinicaltrials.gov/ct2/show/NCT04041882.

Differentiation of insulinoma from accessory spleen by 99mTc-labelled heat-denaturated red blood cell scintigraphy: case report.

BACKGROUND: Neuroendocrine tumors (NETs) are rare tumors harboring overexpression of somatostatin receptors (SSTRs) on their cell membrane. Because some organs, such as the spleen, adrenal glands and liver, physiologically express SSTR, it might be challenging to distinguish some pancreatic NETs located in the pancreatic tail from the accessory spleen next to the splenic hilum. In this manuscript, we report a case with hypoglycemia attack and 2 different masses displayed by Gallium 68-tetraazacyclododecane tetraacetic acid-octreotate (68Ga-DOTATATE) positron emission tomography/computed tomography (PET/CT). CASE PRESENTATION: A 63-year-old woman presented to the hospital with confusion and profuse sweating. Biochemical diagnosis of insulinoma was established. 68Ga-DOTATATE PET/CT revealed two masses with increased tracer uptake located adjacent to the splenic hilum and inferior pole of the spleen which were initially reported as two separate accessory spleens. Then, 99mTc-labelled heat-denaturated red blood cell (99mTc-HDRBC) scintigraphy-single-photon emission computed tomography (SPECT)/CT was performed to distinguish a NET in the pancreatic tail from accessory spleen at the splenic hilum. Enhanced tracer uptake remained in the inferior pole of spleen, but not in the splenic hilum. The lesions were suggestive of insulinoma in the pancreatic tail and an accessory spleen adjacent to the inferior pole of the spleen. CONCLUSION: Approximately 10% of the population have an accessory spleen which can show similar imaging characteristics with pancreatic NETs, especially if located in the pancreatic tail. In our presented case, 99mTc-HDRBC scintigraphy-SPECT/CT is a useful nuclear medicine method to differentiate a NET in the pancreatic tail from accessory spleen at the splenic hilum which may avoid unnecessary surgeries in the presence of enhanced tracer uptake or vice versa.

Nodal metastases in small rectal neuroendocrine tumours.

AIM: Rectal neuroendocrine tumours (NETs) are the most common type of gastrointestinal NET. European Neuroendocrine Tumour Society guidelines suggest that rectal NETs measuring ≤10 mm are indolent with low risk of spread. In practice, many patients with lesions ≤1 cm do not undergo complete tumour staging. However, the size of the lesion may not be the only risk factor for nodal involvement/metastases. The aim of this study was to determine if MRI ± nuclear medicine imaging alters tumour stage in patients with rectal NETs ≤10 mm. METHODS: Patients referred to a tertiary NET centre between 2005 and 2020 who met the inclusion criteria of a rectal NET ≤10 mm, full cross-sectional imaging, primarily an MRI scan and, if abnormal findings were identified, a subsequent 68 Ga-DOTATATE positron emission tomography scan were included. All patients were followed up at our institution. RESULTS: In all, 32 patients with rectal NETs 10 mm or less were included in the study: 16 women; median age 58 years (range 33-71); 47% (n = 15) were referred from bowel cancer screening procedures. The median size of the lesions was 5 mm (range 2-10 mm). 81% (n = 26) were World Health Organization Grade 1 tumours with Ki67 <3%. Radiological staging confirmed nodal involvement in 25% (8/32); two cases had distant metastatic disease. Lymphovascular invasion was present in 3% (1/32) of patients but none demonstrated peri-neural invasion. CONCLUSION: This study demonstrates that small rectal NETs can develop nodal metastases; therefore it is important to stage these tumours accurately with MRI at baseline and, if there are concerns regarding potential lymph node metastases, to consider 68 Ga-DOTATATE positron emission tomography imaging.

Evaluation of 68Ga-DOTATATE uptake at the pituitary region and the biochemical response to somatostatin analogs in acromegaly.

PURPOSE: Acromegaly is associated with many comorbidities and increased mortality. The first-line treatment is transsphenoidal surgery. However, many patients also need adjuvant drug treatment after surgery. Somatostatin analog (SSA), which suppresses GH secretion by somatotrophs by binding to the SSTR2 receptor, is the first choice. Nevertheless, 50% of patients are partially or totally resistant to SSA, so predictive factors of response are helpful to individualize drug treatment. 68GaDOTATATE PET/CT has emerged as the gold-standard method in the diagnosis and follow-up of gastroenteropancreatic neuroendocrine tumors, which also express SSTR. Our objective was to evaluate whether 68Ga-DOTATATE uptake (SUV max) at the pituitary region of patients on SSA therapy would be useful as a drug response predictor without the need of tumoral tissue. METHODS: Fifteen acromegalics patients on SSA treatment for at least 6 months were underwent to 68Ga-DOTATATE PET/CT at the nuclear medicine service. There was an SSA complete response group (n = 5), defined as GH < 1 µg/L and IFG-1 in the normal range for gender and age, and a group that did not meet these criteria (n = 10). RESULTS: As a result, we did not find out a significantly higher SUV max in the complete response group (p = 0.0576) to SSA. However, we found a significant inverse relationship between postoperative GH values and the SUVmax at the sella turcica (p = 0.0188), probably reflecting tumor SSTR2 expression. CONCLUSION: Thus, after this initial evaluation, 68GaDOTATATE PET/CT should be better studied to assess its usefulness in the follow-up of acromegalic patients.

The Clinical Impact of [68 Ga]-DOTATATE PET/CT for the Diagnosis and Management of Ectopic Adrenocorticotropic Hormone - Secreting Tumours.

OBJECTIVES: Localization of ectopic ACTH-secreting tumours causing Cushing syndrome (ECS) is essential for clinical management, yet often difficult. [68 Ga]-DOTATATE PET/CT ([68 Ga]-DOTA-(Tyr3 )-octreotate)] is an FDA-approved high-resolution diagnostic tool for imaging neuroendocrine tumours. Data on the clinical utility of [68 Ga]-DOTATATE in patients with ECS, however, are scarce. The objectives of this study were to determine the efficacy for ECS localization and the clinical benefit of [68 Ga]-DOTATATE imaging. METHOD: We conducted a retrospective review of all cases with ECS evaluated with [68 Ga]-DOTATATE from November 2016 through October 2018 at three referral centres. The clinical benefit of [68 Ga]-DOTATATE was based on detection of new tumours and resultant changes in management. RESULTS: Over the study period, 28 patients with ECS underwent [68 Ga]-DOTATATE: 17 for identification of the primary tumour and 11 during follow-up. [68 Ga]-DOTATATE identified the suspected primary ECS in 11/17 patients (65%). Of these, nine patients underwent surgery: eight with confirmed ECS (5 bronchial, 1 thymic, 1 pancreatic and 1 metastatic neuroendocrine tumour of unknown primary origin) and one patient with a false-positive scan (adrenal gland). Of the 11 patients with ECS who underwent [68 Ga]-DOTATATE evaluation during follow-up, the study led to changes in clinical management in 7/11 (64%) patients. CONCLUSIONS: [68 Ga]-DOTATATE is sensitive in detecting primary and metastatic ECS, often identifies occult tumours after conventional imaging, and impacts clinical care in the majority of patients.