Role of PET/CT in the functional imaging of endocrine pancreatic tumors

Endocrinology application of molecular imaging: current role of PET/CT

BACKGROUND

In recent years, nuclear medicine imaging methods have proven to be of paramount importance in a wide variety of diseases, particularly in oncology, where they are crucial for assessing the extent of disease when conventional methods fall short. Moreover, nuclear imaging modalities are able to better characterize lesions using target agents related to specific pathways (e.g. glucose metabolism, cellular proliferation, amino acid transport, lipid metabolism, specific receptor ligands). The clinical presentation of endocrine diseases encompasses a broad spectrum of sign and symptoms. Moreover, endocrine tumors show varying degrees of aggressiveness from well differentiated and indolent to highly aggressive cancers, respectively.

RATIONALE

With the application of new medicinal radio-compounds and increasingly advanced tomographic imaging technology, the utility of Positron Emission Tomography/Computed Tomography (PET/CT) in the field of endocrine diseases is expanding.

AIM

This review aims to analyze and summarize the primary indications of PET/CT, providing a practical approach for clinicians. A comprehensive literature search on PubMed was conducted to provide an updated overview of the available evidence regarding the use of PET/CT in endocrinology. Within this review, we will discuss the applications of PET/CT, compare different radiopharmaceuticals and highlight the uptake mechanism, excluding neuroendocrine carcinomas from discussion.

CONCLUSIONS

PET/CT is a valuable tool in diagnosing and managing endocrine disorders due to its capacity to furnish both functional and anatomical information, facilitate early lesion detection, guide treatment decisions, and monitor treatment response. Its non-invasive nature and precision make it an integral component of modern endocrine healthcare. This review aims to provide physicians with a clear perspective on the role of PET/CT imaging, discussing its emerging opportunities and appropriateness of use in endocrinological diseases.

[Imaging of pancreatic neuroendocrine tumors]

BACKGROUND

Neuroendocrine tumors of the pancreas have a broad biological spectrum. The treatment decision is based on an optimal diagnosis with regard to the local findings and possible locoregional and distant metastases. In addition to purely morphologic imaging procedures, functional parameters are playing an increasingly important role in imaging.

OBJECTIVES

Prerequisites for optimal imaging of the pancreas, technical principles are provided, and the advantages and disadvantages of common cross-sectional imaging techniques as well as clinical indications for these special imaging methods are discussed.

MATERIALS AND METHODS

Guidelines, basic and review papers will be analyzed.

RESULTS

Neuroendocrine tumors of the pancreas have a broad imaging spectrum. Therefore, there is a need for multimodality imaging in which morphologic and functional techniques support each other. While positron emission tomography/computed tomography (PET/CT) can determine the presence of one or more lesions and its/their functional status of the tumor, magnetic resonance imaging (MRI) efficiently identifies the location, relationship to the main duct and the presence of liver metastases. CT allows a better vascular evaluation, even in the presence of anatomical variants as well as sensitive detection of lung metastases.

CONCLUSIONS

Knowledge of the optimal combination of imaging modalities including clinical and histopathologic results and dedicated imaging techniques is essential to achieve an accurate diagnosis to optimize treatment decision-making and to assess therapy response.

Epidemiology and Prognostic Nomogram for Predicting Long-Term Disease-Specific Survival in Patients With Pancreatic Carcinoid Tumor: A SEER-Based Study

OBJECTIVES

Pancreatic carcinoid tumor (PCT) is described as a malignant form of carcinoid tumors. However, the epidemiology and prognostic factors for PCT are poorly understood.

MATERIALS AND METHODS

The data of 2447 PCT patients were included in this study from the Surveillance, Epidemiology, and End Results database and randomly divided into a training cohort (1959) and a validation cohort (488). The epidemiology of PCT was calculated, and independent prognostic factors were identified to construct a prognostic nomogram for predicting long-term disease-specific survival (DSS) among PCT patients.

RESULTS

The incidence of PCT increased remarkably from 2000 to 2018. The 1-, 5-, and 10-year DSS rates were 96.4%, 90.3%, and 86.5%, respectively. Age at diagnosis, stage, surgery, radiotherapy, and chemotherapy were identified as independent prognostic factors to construct a prognostic nomogram. The C -indices; area under the receiver operating characteristic curves for predicting 1-, 5-, and 10-year DSS, and calibration plots of the nomogram in both cohorts indicated a high discriminatory accuracy, preferable survival predictive ability, and optimal concordances, respectively.

CONCLUSIONS

The incidence of PCT has increased rapidly since 2000. In addition, we established a practical, effective, and accurate prognostic nomogram for predicting the long-term DSS of PCT patients.

Diagnostic accuracy of SSR-PET/CT compared to histopathology in the identification of liver metastases from well-differentiated neuroendocrine tumors

BACKGROUND

Histopathology is the reference standard for diagnosing liver metastases of neuroendocrine tumors (NETs). Somatostatin receptor-positron emission tomography / computed tomography (SSR-PET/CT) has emerged as a promising non-invasive imaging modality for staging NETs. We aimed to assess the diagnostic accuracy of SSR-PET/CT in the identification of liver metastases in patients with proven NETs compared to histopathology.

METHODS

Histopathologic reports of 139 resected or biopsied liver lesions of patients with known NET were correlated with matching SSR-PET/CTs and the positive/negative predictive value (PPV/NPV), sensitivity, specificity, and diagnostic accuracy of SSR-PET/CT were evaluated. PET/CT reading was performed by one expert reader blinded to histopathology and clinical data.

RESULTS

133 of 139 (95.7%) liver lesions showed malignant SSR-uptake in PET/CT while initial histopathology reported on 'liver metastases of NET´ in 127 (91.4%) cases, giving a PPV of 91.0%. Re-biopsy of the initially histopathologically negative lesions (reference standard) nevertheless diagnosed 'liver metastases of NET' in 6 cases, improving the PPV of PET/CT to 95.5%. Reasons for initial false-negative histopathology were inadequate sampling in the sense of non-target biopsies. The 6 (4.3%) SSR-negative lesions were all G2 NETs with a Ki-67 between 2-15%.

CONCLUSION

SSR-PET/CT is a highly accurate imaging modality for the diagnosis of liver metastases in patients with proven NETs. However, we found that due to the well-known tumor heterogeneity of NETs, specifically in G2 NETs approximately 4-5% are SSR-negative and may require additional imaging with [18F]FDG PET/CT.

Diagnostic performance of PET/CT in the detection of liver metastases in well-differentiated NETs

BACKGROUND

The aim of this retrospective study was to compare the diagnostic accuracy of somatostatin receptor (SSR)-PET/CT to liver MRI as reference standard in the evaluation of hepatic involvement in neuroendocrine tumors (NET).

METHODS

An institutional database was screened for "SSR" imaging studies between 2006 and 2021. 1000 NET Patients (grade 1/2) with 2383 SSR-PET/CT studies and matching liver MRI in an interval of +3 months were identified. Medical reports of SSR-PET/CT and MRI were retrospectively evaluated regarding hepatic involvement and either confirmed by both or observed in MRI but not in SSR-PET/CT (false-negative) or in SSR-PET but not in MRI (false-positive).

RESULTS

Metastatic hepatic involvement was reported in 1650 (69.2%) of the total 2383 SSR-PET/CT imaging studies, whereas MRI detected hepatic involvement in 1685 (70.7%) cases. There were 51 (2.1%) false-negative and 16 (0.7%) false-positive cases. In case of discrepant reports, MRI and PET/CT were reviewed side by side for consensus reading. SSR-PET/CT demonstrated a sensitivity of 97.0% (95%CI: 96.0%, 97.7%), a specificity of 97.7% (95%CI: 96.3%, 98.7%), a PPV of 99.0% (95%CI: 98.4%, 99.4%) and NPV of 93.0% (95%CI: 91.0, 94.8%) in identifying hepatic involvement. The most frequent reason for false-negative results was the small size of lesions with the majority < 0.6 cm.

CONCLUSION

This study confirms the high diagnostic accuracy of SSR-PET/CT in the detection of hepatic involvement in NET patients based on a patient-based analysis of metastatic hepatic involvement with a high sensitivity and specificity using liver MRI imaging as reference standard. However, one should be aware of possible pitfalls when a single imaging method is used in evaluating neuroendocrine liver metastases in patients.

Diagnostic Management of Gastroenteropancreatic Neuroendocrine Neoplasms: Technique Optimization and Tips and Tricks for Radiologists

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) comprise a heterogeneous group of neoplasms, which derive from cells of the diffuse neuroendocrine system that specializes in producing hormones and neuropeptides and arise in most cases sporadically and, to a lesser extent, in the context of complex genetic syndromes. Furthermore, they are primarily nonfunctioning, while, in the case of insulinomas, gastrinomas, glucagonomas, vipomas, and somatostatinomas, they produce hormones responsible for clinical syndromes. The GEP-NEN tumor grade and cell differentiation may result in different clinical behaviors and prognoses, with grade one (G1) and grade two (G2) neuroendocrine tumors showing a more favorable outcome than grade three (G3) NET and neuroendocrine carcinoma. Two critical issues should be considered in the NEN diagnostic workup: first, the need to identify the presence of the tumor, and, second, to define the primary site and evaluate regional and distant metastases. Indeed, the primary site, stage, grade, and function are prognostic factors that the radiologist should evaluate to guide prognosis and management. The correct diagnostic management of the patient includes a combination of morphological and functional evaluations. Concerning morphological evaluations, according to the consensus guidelines of the European Neuroendocrine Tumor Society (ENETS), computed tomography (CT) with a contrast medium is recommended. Contrast-enhanced magnetic resonance imaging (MRI), including diffusion-weighted imaging (DWI), is usually indicated for use to evaluate the liver, pancreas, brain, and bones. Ultrasonography (US) is often helpful in the initial diagnosis of liver metastases, and contrast-enhanced ultrasound (CEUS) can solve problems in characterizing the liver, as this tool can guide the biopsy of liver lesions. In addition, intraoperative ultrasound is an effective tool during surgical procedures. Positron emission tomography (PET-CT) with FDG for nonfunctioning lesions and somatostatin analogs for functional lesions are very useful for identifying and evaluating metabolic receptors. The detection of heterogeneity in somatostatin receptor (SSTR) expression is also crucial for treatment decision making. In this narrative review, we have described the role of morphological and functional imaging tools in the assessment of GEP-NENs according to current major guidelines.

Diagnosis and management of gastroenteropancreatic neuroendocrine neoplasms by nuclear medicine: Update and future perspective

Gastrointestinal (GI) cancers are the second most common cause of cancer related deaths in the World. Neuroendocrine neoplasms (NENs) is a rare tumor that originated from peptidergic neurons and neuroendocrine cells. NENs occurs in all parts of the body, especially in stomach, intestine, pancreas and lung. These rare tumors are challenging to diagnose at earlier stages because of their wide anatomical distribution and complex clinical features. Traditional imaging methods including magnetic resonance imaging (MRI) and computed tomography (CT) are mostly of useful for detection of larger primary tumors that are 1cm in size. A new medical imaging specialty called nuclear medicine uses radioactive substances for both diagnostic and therapeutic purposes. Nuclear medicine imaging relies on the tissue-specific uptake of radiolabeled tracers. Nuclear medicine techniques can easily identify the NENs tissues for their ability to absorb and concentrate amine, precursors, and peptides, whereas the traditional imaging methods are difficult to perform well. The somatostatin receptor (SSTR) is a targetable receptor frequently expressed in the gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs), and is a promising target for tumor-targeted therapies and radiography. SSTR based somatostatin receptor imaging and peptide receptor radionuclide therapy (PRRT) has emerged as a new hot subject in the diagnosis and treatment of GEP-NENs due to the rapid development of somatostatin analogues (SSAs) and radionuclide. This review aims to provide an overview of the current status of nuclear medicine imaging modalities in the imaging of GEP-NENs, and puts them in perspective of clinical practice.

Nuclear Medicine and Radiological Imaging of Pancreatic Neuroendocrine Neoplasms: A Multidisciplinary Update

Pancreatic neuroendocrine neoplasms (panNENs) are part of a large family of tumors arising from the neuroendocrine system. PanNENs show low-intermediate tumor grade and generally high somatostatin receptor (SSTR) expression. Therefore, panNENs benefit from functional imaging with ⁶⁸Ga-somatostatin analogues (SSA) for diagnosis, staging, and treatment choice in parallel with morphological imaging. This narrative review aims to present conventional imaging techniques and new perspectives in the management of panNENs, providing the clinicians with useful insight for clinical practice. The ⁶⁸Ga-SSA PET/CT is the most widely used in panNENs, not only fr diagnosis and staging purpose but also to characterize the biology of the tumor and its responsiveness to SSAs. On the contrary, the ¹⁸F-Fluordeoxiglucose (FDG) PET/CT is not employed systematically in all panNEN patients, being generally preferred in G2-G3, to predict aggressiveness and progression rate. The combination of ⁶⁸Ga-SSA PET/CT and ¹⁸F-FDG PET/CT can finally suggest the best therapeutic strategy. Other radiopharmaceuticals are ⁶⁸Ga-exendin-4 in case of insulinomas and ¹⁸F-dopamine (DOPA), which can be helpful in SSTR-negative tumors. New promising but still-under-investigation radiopharmaceuticals include radiolabeled SSTR antagonists and ¹⁸F-SSAs. Conventional imaging includes contrast enhanced CT and multiparametric MRI. There are now enriched by radiomics, a new non-invasive imaging approach, very promising to early predict tumor response or progression.

Integration of molecular imaging in the personalized approach to neuroendocrine tumors

NETs lesions can be difficult to characterize with conventional anatomic imaging (CT and MRI). Functional imaging techniques, and especially PET imaging, are very useful for detecting small neuroendocrine tumors that would not be seen with other techniques. The role of nuclear medicine in the localization, staging, restaging, treatment and monitoring of neuroendocrine tumors (NETs) has become progressively more relevant due to: the availability of tracers on new targets, tracers for positron emission tomography (PET); the development of cyclotrons and generators that allow this availability; as well as to hybrid systems (SPECT/CT, PET/CT and PET/MRI) that, by joining the functional and anatomical image, improve the quality of the images. Teragnosis, a new emerging therapy, in NET used receptor-mediated or nonreceptor- mediated mechanism to facilitate penetration and high-affinity binding between the radiopharmaceutical and the tumor cell. Teragnosis offers the possibility of personalized targeted radionuclide therapy.

Role of PET/CT and Therapy Management of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine neoplasms (panNENs) are heterogeneous neoplasms with neuroendocrine differentiation that show peculiar clinical and histomorphological features, with variable prognosis. In recent years, advances in knowledge regarding the pathophysiology and heterogeneous clinical presentation, as well as the availability of different diagnostic procedures for panNEN diagnosis and novel therapeutic options for patient clinical management, has led to the recognition of the need for an active multidisciplinary discussion for optimal patient care. Molecular imaging with positron emission tomography/computed tomography (PET/CT) has become indispensable for the management of panNENs. Several PET radiopharmaceuticals can be used to characterize either panNEN receptor expression or metabolism. The aim of this review is to offer an overview of all the currently used radiopharmaceuticals and of the new upcoming tracers for pancreatic neuroendocrine tumors (panNETs), and their clinical impact on therapy management. [68Ga]Ga-DOTA-peptide PET/CT (SSA-PET/CT) has high sensitivity, specificity, and accuracy and is recommended for the staging and restaging of any non-insulinoma well-differentiated panNEN cases to carry out detection of unknown primary tumor sites or early relapse and for evaluation of in vivo somatostatin receptors expression (SRE) to select patient candidates for peptide receptor radiometabolic treatment (PRRT) with 90Y or 177Lu and/or cold analogs. SSA-PET/CT also has a strong impact on clinical management, leading to a change in treatment in approximately a third of the cases. Its role for treatment response assessment is still under debate due to the lack of standardized criteria, even though some semiquantitative parameters seem to be able to predict response. [18F]FDG PET/CT generally shows low sensitivity in small growing and well-differentiated neuroendocrine tumors (NET; G1 and G2), while it is of utmost importance in the evaluation and management of high-grade NENs and also provides important prognostic information. When positive, [18F]FDG PET/CT impacts therapeutical management, indicating the need for a more aggressive treatment regime. Although FDG positivity does not exclude the patient from PRRT, several studies have demonstrated that it is certainly useful to predict response, even in this setting. The role of [18F]FDOPA for the study of panNET is limited by physiological uptake in the pancreas and is therefore not recommended. Moreover, it provides no information on SRE that has crucial clinical management relevance. Early acquisition of the abdomen and premedication with carbidopa may be useful to increase the accuracy, but further studies are needed to clarify its utility. GLP-1R agonists, such as exendin-4, are particularly useful for benign insulinoma detection, but their accuracy decreases in the case of malignant insulinomas. Being a whole-body imaging technique, exendin-PET/CT gives important preoperative information on tumor size and localization, which is fundamental for surgical planning as resection (enucleation of the lesion or partial pancreatic resection) is the only curative treatment. New upcoming tracers are under study, such as promising SSTR antagonists, which show a favorable biodistribution and higher tumor-to-background ratio that increases tumor detection, especially in the liver. [68Ga]pentixafor, an in vivo marker of CXCR4 expression associated with the behavior of more aggressive tumors, seems to only play a limited role in detecting well-differentiated NET since there is an inverse expression of SSTR2 and CXCR4 in G1 to G3 NETs with an elevation in CXCR4 and a decrease in SSTR2 expression with increasing grade. Other tracers, such as [68Ga]Ga-PSMA, [68Ga]Ga-DATA-TOC, [18F]SiTATE, and [18F]AlF-OC, are also under investigation.

The impact of 18F-FDOPA-PET/MRI image fusion in detecting liver metastasis in patients with neuroendocrine tumors of the gastrointestinal tract

Background

This study assesses the value of image fusion using 18F-fluoro-L-DOPA (18F-DOPA) positron emission tomography (PET) and magnetic resonance imaging (MRI) for examining patients with neuroendocrine tumors (NETs) and a suspicion of metastasis of the liver.

Methods

Eleven patients (five women and six men aged between 20 and 81, with a mean age of 54.6 years) were included in the study. All patients underwent whole-body 18F-DOPA PET examinations and contrast-enhanced MRI with diffusion-weighted sequences (DWS). Image fusion was performed using a semiautomatic voxel-based algorithm. Images obtained using PET and MRI were assessed separately. Side-by-side evaluations of fused PET/MRI images were also performed.

Results

In total, 55 liver lesions (52 liver metastases and 3 benign lesions) were detected in the 11 patients. Sensitivity detection for liver lesions was higher when using PET/CT than when using contrast-enhanced MRI without DWSs and lower than using MRI with DWSs. The sensitivity of PET/MRI image fusion in the detection of liver metastasis was significantly higher than that of MRI with DWSs (P < 0.05).

Conclusion

Images of the liver obtained using PET and MRI in patients with NETs exhibited characteristic features. These findings suggest that an appropriate combination of available imaging modalities can optimize patient evaluations.

Diagnostic utility of Gallium-68-somatostatin receptor PET/CT in ectopic ACTH-secreting tumors: a systematic literature review and single-center clinical experience

PURPOSE

Tumors causing ectopic Cushing's syndrome (ECS) are often not visible with conventional imaging. Gallium-68-DOTATATE, DOTATOC, and DOTANOC positron emission tomography/computed tomography (⁶⁸Ga-SSTR PET/CT) reportedly exhibits greater sensitivity in identifying an ECS source, however, evidence is limited to mainly case reports and a few small retrospective studies. Previous systematic ECS imaging review has shown ⁶⁸Ga-SSTR PET/CT sensitivity is similar to CT (81.8%) in histologically-proven cases and is 100% in covert-cases, however, the number of patients was small and no occult cases were reported.

METHODS

We performed a systematic literature review of ⁶⁸Ga-SSTR PET/CT use in ECS patients. We also report 6 consecutive patients with confirmed active and occult ECS who underwent ⁶⁸Ga-DOTATATE PET/CT and were followed at our institution between 2014 and 2019.

RESULTS

We identified 33 articles (23 case-reports, 4 case-series, 5 retrospective studies and 1 prospective study) detailing ⁶⁸Ga-SSTR PET/CT in 69 ECS patients. Overall ⁶⁸Ga-SSTR PET/CT sensitivity was 64.0%, while in histologically confirmed cases (67 lesions), sensitivity was 76.1%. There were two false-positives cases, both in the adrenal glands. In covert cases, ⁶⁸Ga-SSTR PET/CT identified 50% of lesions. There were ten occult cases where all imaging failed to identify an adrenocorticotropic hormone source; source remains unknown. In our case series, ⁶⁸Ga-DOTATATE PET/CT showed decreased uptake in pancreatic neuroendocrine tumor in one patient and did not help identify an ECS source in 5 patients.

CONCLUSION

Both this systematic literature review, the largest to date, and our single- center experience demonstrate a lower than previously reported ⁶⁸Ga-SSTR PET/CT sensitivity for ECS, especially in occult lesions. We suggest that the data on ⁶⁸Ga-SSTR PET/CT in ECS is subject to publication bias, and false-negatives are likely underreported; it's diagnostic value for ECS needs further study.

Vasoactive Intestinal Peptide-Secreting Tumors: A Review

Vasoactive intestinal peptide-secreting tumors (VIPomas) are a group of rare neuroendocrine tumors, which cause a typical syndrome of watery diarrhea. Most of these tumors are found in the pancreas and are usually detected at a later stage. Although curative resection is not possible in most of these tumors, both symptom and tumor control can be achieved by a multidimensional approach, to enable a long survival of most patients. There are no clear-cut guidelines for the management of VIPomas because of the rarity of this neoplasm and lack of prospective data. In this review, we discuss the available evidence on the clinical features and management of these rare tumors.

Peptide Receptor Radionuclide Therapy in Grade 3 Neuroendocrine Neoplasms: Safety and Survival Analysis in 69 Patients

To date, limited data are available concerning peptide receptor radionuclide therapy (PRRT) of grade 3 (G3) neuroendocrine neoplasms (NENs) with a Ki-67 proliferation index of greater than 20%. The purpose of this study was to analyze the long-term outcome, efficacy, and safety of PRRT in patients with somatostatin receptor (SSTR)-expressing G3 NENs. Methods: A total of 69 patients (41 men; age, 28-81 y) received PRRT with ¹⁷⁷Lu- or ⁹⁰Y-labeled somatostatin analogs (DOTATATE or DOTATOC). Twenty-two patients had radiosensitizing chemotherapy. Kaplan-Meier analysis was performed to calculate progression-free survival (PFS) and overall survival (OS), defined from the start of PRRT, including a subgroup analysis for patients with a Ki-67 index of less than or equal to 55% and a Ki-67 index of greater than 55%. Treatment response was evaluated according to RECIST 1.1 as well as molecular imaging criteria (European Organization for Research and Treatment of Cancer). Short- and long-term toxicity was documented (Common Terminology Criteria for Adverse Events, v 5.0) using a structured database (comprising >250 items per patient) and retrospectively analyzed. Results: Forty-six patients had pancreatic NENs, 11 had unknown primary cancer, 6 had midgut NENs, 3 had gastric NENs, and 3 had rectal NENs. The median follow-up was 94.3 mo. The median PFS was 9.6 mo, and the median OS was 19.9 mo. For G3 NENs with a Ki-67 index of less than or equal to 55% (n = 53), the median PFS was 11 mo and the median OS was 22 mo. Patients with a Ki-67 index of greater than 55% (n = 11) had a median PFS of 4 mo and a median OS of 7 mo. For patients with positive SSTR imaging but no ¹⁸F-FDG uptake, the median PFS was 24 mo and the median OS was 42 mo. A significant difference was found for both PFS and OS, with median PFS of 16 mo and 5 mo and median OS of 27 mo and 9 mo for an SUV_max of greater than 15.0 and an SUV_max of less than or equal to 15.0, respectively, on SSTR PET. In the group with ¹⁸F-FDG uptake scored as 3 or 4, the median PFS was 7.1 mo and the median OS was 17.2 mo. In the group with ¹⁸F-FDG uptake scored as 0-2, the median PFS was 24.3 mo and the median OS was 41.6 mo. PRRT was well tolerated by all patients; no grade 3 or grade 4 hematotoxicity occurred, and no clinically significant decline in renal function was observed. There was no hepatotoxicity. Conclusion: PRRT was tolerated well, without significant adverse effects, and was efficacious in G3 NENs; the clinical outcome was promising, especially in patients with a Ki-67 index of less than or equal to 55% and even in patients for whom chemotherapy had failed. Baseline ¹⁸F-FDG along with SSTR molecular imaging was useful for stratifying G3 NEN patients with high uptake on SSTR PET/CT and no or minor ¹⁸F-FDG avidity-a mismatch pattern that was associated with a better long-term prognosis.

Imaging in a rare case of neuroendocrine tumour with skin metastases

Purpose

Disseminated malignancies are a diagnostic and therapeutic challenge that is often encountered in radiology. Finding the primary tumour is crucial for planning proper surgical and oncological treatment. Computed tomography (CT) of the thorax and abdomen is typically the initial examination. However, abdominal magnetic resonance imaging (MRI) or positron emission tomography (PET/CT) or PET/MRI are often subsequently performed. Histopathological examination of metastatic tumours is performed as well, followed by immunohistochemistry. The aim of the report was to present diagnostic workup in a rare case of skin metastases.

Case report

A 72-year-old patient was admitted to a dermatology ward because of skin lesions – violaceous nodules localised on the hair-covered skin of the head. On abdominal CT, a generalised neoplastic process with metastases in the liver, pancreas, adrenal glands, lymph nodes, bones, thoracic wall, and a suspected metastasis in the right breast was revealed. Histopathology of the skin nodules confirmed a neuroendocrine tumour. Metastases of a pancreatic neuroendocrine tumour or small-cell lung cancer were suspected on immunohistochemistry. The patient died before we were able to localise the primary source of the tumour and provide treatment.

Conclusions

Skin metastases are relatively rare, aggravate the prognosis, and usually indicate spread of the neoplastic process in the internal organs. It is not always possible to localise the primary tumour using radiological imaging. In such cases, co-operation with the pathologist is crucial as are the results of histopathological and immunohistochemical examinations.

Increased Expression of GLP-1R in Proliferating Islets of Men1 Mice is Detectable by [68Ga]Ga-DO3A-VS-Cys40-Exendin-4 /PET

Multiple endocrine neoplasia type 1 (MEN1) is an endocrine tumor syndrome caused by heterozygous mutations in the MEN1 tumor suppressor gene. The MEN1 pancreas of the adolescent gene carrier frequently contain diffusely spread pre-neoplasias and microadenomas, progressing to macroscopic and potentially malignant pancreatic neuroendocrine tumors (P-NET), which represents the major death cause in MEN1. The unveiling of the molecular mechanism of P-NET which is not currently understood fully to allow the optimization of diagnostics and treatment. Glucagon-like peptide 1 (GLP-1) pathway is essential in islet regeneration, i.e. inhibition of β-cell apoptosis and enhancement of β-cell proliferation, yet involvement of GLP-1 in MEN1 related P-NET has not yet been demonstrated. The objective of this work was to investigate if normal sized islets of Men1 heterozygous mice have increased Glucagon-like peptide-1 receptor (GLP-1R) expression compared to wild type islets, and if this increase is detectable in vivo with positron emission tomography (PET) using [68Ga]Ga-DO3A-VS-Cys40-Exendin-4 (68Ga-Exendin-4). 68Ga-Exendin-4 showed potential for early lesion detection in MEN1 pancreas due to increased GLP1R expression.

The Accessory Spleen Is an Important Pitfall of 68Ga-DOTANOC PET/CT in the Workup for Pancreatic Neuroendocrine Neoplasm

OBJECTIVE

The aim of the study was to assess the value and potential pitfalls of Ga-DOTANOC positron emission tomography/computed tomography (PET/CT) in patients with suspected pancreatic neuroendocrine neoplasms (pNEN).

METHODS

Consecutive patients referred for Ga-DOTANOC PET/CT for suspected pNEN between May 1, 2011, and October 31, 2014, were retrospectively assessed. Scan data were compared with cytological/histological final diagnosis. Pancreatic neuroendocrine neoplasm detection rate was determined on per-patient and per-lesion basis. Maximum standardized uptake values of lesions were determined.

RESULTS

Fifty-eight patients with 65 lesions were enrolled. Twelve patients had nonconfirmed diagnosis; of these, 7 were positive and 5 negative at PET/CT. Of 46 patients with confirmed diagnosis, 36 had pNEN; of these, 33 were positive, 1 negative, and 2 nonevaluable at PET/CT. Ten patients had non-NE lesions, of which 8 were positive, 1 negative, and 1 nonevaluable at PET/CT. Of 48 patients with positive PET/CT, 8 proved to have non-NE lesions, of which 6 were intrapancreatic accessory spleen. No significant maximum standardized uptake values difference was found between pNEN and non-NE lesions.

CONCLUSIONS

Intrapancreatic accessory spleen is an important pitfall in Ga-DOTANOC PET/CT for suspected pNEN. Cytological/histological confirmation is mandatory before any surgical procedure is undertaken.

Pancreatic Uptake by 18F-FDOPA PET/CT in Patients With Hypoglycemia After Gastric Bypass Surgery Compared With Controls With or Without Carbidopa Pretreatment

PURPOSE

The use of Fluorine-labeled dihydroxy-phenyl-alanine (F-FDOPA) PET/CT in patients with hypoglycemia suspected to be caused by pancreatic disease can be helpful to localize the source of excess insulin production. In this setting, carbidopa pretreatment is not recommended. However, quantitative comparisons of pancreatic tracer uptake in patients with or without carbidopa pretreatment and in diffuse pancreatic disease are lacking. Therefore, we aimed to describe and quantify pancreatic F-FDOPA uptake in patients without pancreatic disease with or without carbidopa pretreatment and in patients with hypoglycemia after gastric bypass surgery.

PATIENTS AND METHODS

This is a retrospective data analysis of F-FDOPA PET/CT scans performed at a university medical center in the period from 2009 to 2015. All scans were reconstructed and calculated based on the European Association of Nuclear Medicine/EANM Research Ltd guidelines. Of 358 patients without evidence of pancreatic disease or hypoglycemic disorders, 344 received carbidopa and 14 did not. Another 9 patients had post-gastric bypass hypoglycemia. The main outcome measurement was F-FDOPA SUVmax for pancreatic head, body, and tail regions.

RESULTS

Carbidopa pretreated patients had a lower median SUVmax (-1.15, -1.20, and -0.84 in pancreatic head, body, and tail [all P < 0.01]) than patients without carbidopa pretreatment. Patients with post-gastric bypass hypoglycemia scanned without carbidopa pretreatment had higher median SUVmax (+1.18, +1.39, and +1.63, all P < 0.03) compared with controls without pretreatment.

CONCLUSIONS

Patients with post-gastric bypass hypoglycemia have increased uptake in all pancreatic regions. Carbidopa pretreatment lowers pancreatic F-FDOPA uptake in the nonaffected pancreas and may therefore mask disease activity in post-gastric bypass hypoglycemia.

Management of neuroendocrine carcinomas of the pancreas (WHO G3): A tailored approach between proliferation and morphology

Neuroendocrine carcinomas (NEC) of the pancreas are defined by a mitotic count > 20 mitoses/10 high power fields and/or Ki67 index > 20%, and included all the tumors previously classified as poorly differentiated endocrine carcinomas. These latter are aggressive malignancies with a high propensity for distant metastases and poor prognosis, and they can be further divided into small- and large-cell subtypes. However in the NEC category are included also neuroendocrine tumors with a well differentiated morphology but ki67 index > 20%. This category is associated with better prognosis and does not significantly respond to cisplatin-based chemotherapy, which represents the gold standard therapeutic approach for poorly differentiated NEC. In this review, the differences between well differentiated and poorly differentiated NEC are discussed considering both pathology, imaging features, treatment and prognostic implications. Diagnostic and therapeutic flowcharts are proposed. The need for a revision of current classification system is stressed being well differentiated NEC a more indolent disease compared to poorly differentiated tumors.

68Ga-DOTATATE PET in juvenile angiofibroma

Background: As somatostatin receptors (SSTRs) may be overexpressed in rapidly growing vessels, the aim of this study was the analysis of in vivo and in vitro SSTR2A expression in juvenile angiofibroma (JA). Material & methods: A group of six male adolescents with a diagnosis of primary, recurrent/residual JA was enrolled in the study. All patients underwent 68Ga-DOTATATE PET/computed tomography (CT) followed by immunohistochemical staining for SSTR expression. Results: 68Ga-DOTATATE PET/CT showed accumulation in areas matching the pathologic tissue in the nasopharynx of all patients studied with SUVmax of 5.1 ± 0.9 (ranging from 3.6 to 6.4). In all cases, the immunohistochemical examination showed a presence of SSTR2A with a high staining index. Conclusion: In vitro SSTR2A cytoplasm expression was found to be high in all tumor specimens. However, the uptake of 68Ga-DOTATATE was weak in the PET/CT studies. We postulate that the intracellular localization of the SSTR2A in JA may cause this discrepancy.

Predictive prognostic value of local and distant recurrence of F-fluorodeoxyglucose positron emission tomography for pancreatic neuroendocrine tumors with reference to World Health Organization classifications (2004, 2010). Case series study

BACKGROUND

F-flurodeoxyglucose positron emission tomography (FDG-PET) have been claimed to be an important prognostic tool in different malignancies. However, its predictive prognostic value on pancreatic neuroendocrine tumors (PNETs) is still under investigation.

AIM

We study the prognostic impact of FDG-PET scan in neuroendocrine pancreatic tumors.

METHODOLOGY

Between 2007 and 2012, 26 patients with no metastastatic histologically confirmed PNETs (mean age: 57 years) were examined with FDG-PET. We studied its captation in relation with the well established hystopathological prognostic markers assessed in the tumoral resected specimen according to the WHO 2004 and ENETS/WHO 2010 classification.

RESULTS

FDG-PET captation was positive in 17 cases (65.4%). The median follow-up period was 34.4 months and recurrences occurred in 4 cases (15.4%). We found a significant correlation between this captation and Ki 67 index (p = 0.032), mitotic index (p = 0.002), tumor grade (p = 0.017) and tumor size (p = 0.01).

CONCLUSIONS

FDG-PET provides a good prognostic value for PNETs. Present results must be further validated with larger sample studies.

Effectiveness and side-effects of peptide receptor radionuclide therapy for neuroendocrine neoplasms in Germany: A multi-institutional registry study with prospective follow-up

BACKGROUND

Monocentric and retrospective studies indicate effectiveness of peptide receptor radionuclide therapy targeting somatostatin receptors of neuroendocrine neoplasms. We assessed overall and progression-free survival and adverse events of peptide receptor radionuclide therapy by a multi-institutional, board certified registry with prospective follow-up in five centres in Germany.

METHODS

A total of 450 patients were included and followed for a mean of 24.4 months. Most patients had progressive low- or intermediate grade neuroendocrine neoplasms and 73% were pretreated with at least one therapy. Primary neuroendocrine neoplasms were mainly derived of pancreas (38%), small bowel (30%), unknown primary (19%) or bronchial system (4%). Patients were treated with Lutetium-177 in 54%, with Yttrium-90 in 17% and with both radionuclides in 29%. Overall and progression-free survival was determined with Kaplan-Meier curves and uni-variate log rank test Cox models.

FINDINGS

Median overall survival of all patients was 59 (95% confidence interval [CI] 49-68.9) months. Overall survival was significantly inferior in the patients treated with Yttrium-90 solely (hazard ratio, 3.22; 95% CI, 1.83-5.64) compared to any peptide receptor radionuclide therapy with Lutetium-177. Grade II (hazard ratio, 2.06; 95% CI, 0.79-5.32) and grade III (hazard ratio, 4.22; 95% CI, 1.41-12.06) neuroendocrine neoplasms had significantly worse overall survival than grade I neuroendocrine neoplasms. Patients with small neuroendocrine neoplasms of small bowel had significantly increased survival (hazard ratio, 0.39; 95% CI, 0.18-0.87) compared to neuroendocrine neoplasms of other locations. Median progression-free survival was 41 (35.9-46.1) months and significantly inferior in patients treated with Yttrium solely (hazard ratio, 2.7; 95% CI, 1.71-4.55). Complete remission was observed in 5.6% of patients, 22.4% had a partial remission, 47.3% were stable and 4% were progressive as best response. Adverse events of bone marrow and kidney function higher than grade III occurred in 0.2-1.5% of patients.

INTERPRETATION

These results indicate that peptide receptor radionuclide therapy is a highly effective therapy for patients with low to intermediate grade neuroendocrine neoplasms with minor adverse events.

Evaluation of the Added Value of Diffusion-Weighted Imaging to Conventional Magnetic Resonance Imaging in Pancreatic Neuroendocrine Tumors and Comparison With 68Ga-DOTANOC Positron Emission Tomography/Computed Tomography

OBJECTIVES

The aims of this study were to investigate the added value of diffusion-weighted imaging (DWI) in pancreatic neuroendocrine tumor (pNET) evaluation and to compare magnetic resonance imaging (MRI) to Ga-DOTANOC positron emission tomography/computed tomography (PET/CT) results.

METHODS

Morphological MRI (T2-weighted [T2-w] + contrast-enhanced [CE] T1-w) and DWI (T2-w + DWI) and Ga-DOTANOC PET/CT in 25 patients/30 pNETs were retrospectively evaluated. Per-patient and per-lesion detection rates (pDR and lDR, respectively) were calculated. Apparent diffusion coefficient values were compared among pNET and surrounding and normal pancreas (control group, 18 patients). Apparent diffusion coefficient and standardized uptake value (SUV) values were compared among different grading and staging groups.

RESULTS

No statistically significant differences in PET/CT and MRI session detection rates were found (morphological MRI and DW-MRI, 88% pDR and 87% lDR; combined evaluation, 92% pDR and 90% lDR; Ga-DOTANOC PET/CT, 88% pDR and 80% lDR). Consensus reading (morphological/DW-MRI + PET/CT) improved pDR and lDR (100%). Apparent diffusion coefficient mean value was significantly lower compared with surrounding and normal parenchyma (P < 0.01). The apparent diffusion coefficient and SUV values of pNETs among different grading and staging groups were not statistically different.

CONCLUSIONS

Conventional MRI, DW-MRI + T2-w sequences, and Ga-DOTANOC PET/CT can be alternative tools in pNET detection. Diffusion-weighted MRI could be valuable in patients with clinical suspicion but negative conventional imaging findings. However, the consensus reading of the 3 techniques seems the best approach.

Role of (68)Ga somatostatin receptor PET/CT in the detection of endogenous hyperinsulinaemic focus: an explorative study

PURPOSE

To explore the role of (68)Ga-DOTATATE/DOTATOC PET/CT (SR PET/CT) in patients with suspicion of or histopathologically proven pancreatogenic hyperinsulinaemic hypoglycaemia.

METHODS

We included 13 patients with histopathologically proven or a high clinical suspicion of pancreatogenic hyperinsulinaemia. All the patients underwent a SR PET/CT scan. The results were correlated with histopathological findings. Normalization of blood glucose levels after resection of the pancreatic lesion, as well as a cytological and/or pathological diagnosis of insulinoma, was considered the diagnostic gold standard for insulinoma. The diagnosis of nesidioblastosis was based on exclusion of an insulinoma and conclusive pathological examination of a segment of the pancreas. Malignant insulinoma was defined as the presence of locoregional or distant metastases.

RESULTS

Based on histopathology, 13 patients were found to have pancreatic hyperinsulinaemia: two patients had malignant insulinoma, eight had nonmetastasized insulinoma, and three had nesidioblastosis. SR PET was positive in 11 of the 13 patients (84.6 %) with a final diagnosis of endogenous pancreatic hypoglycaemia. Histopathological staining confirmed 16 foci of hyperinsulinism (insulin positivity). SR PET detected 14 of the 16 lesions, resulting in a sensitivity of 87 %. One intrapancreatic spleen was falsely diagnosed as insulinoma focus on SR PET, resulting in positive predictive value of 93.3 %. Immunohistochemical staining of somatostatin receptor (SSR) subtype 2a was available in ten specimens: two nesidioblastosis, and seven benign and one malignant insulinoma. Eight out of the ten specimens (80 %) stained strongly to moderately positive. Seven of the eight SSR2a-positive lesions were picked up on SR PET. Based on the results of SR PET/CT, nine patients achieved complete remission of the hypoglycaemic events during follow-up.

CONCLUSION

This explorative study suggests that SR PET in combination with CT may play a significant role in the detection and management of patients with pancreatogenic hyperinsulinaemic hypoglycaemia. A large proportion of insulinomas express SSR2a, and a larger study is needed to fully assess the diagnostic accuracy of SR PET in patients with insulinoma and nesidioblastosis compared with current localizing studies used in clinical practice.

Pancreatic Neuroendocrine Tumors: an Update

Pancreatic neuroendocrine tumors (pNETs) are rare and comprise only 1-2 % of all pancreatic neoplastic disease. Although the majority of these tumors are sporadic (90 %), pNETs can arise in the setting of several different hereditary genetic syndromes, most commonly multiple endocrine neoplasia type 1 (MEN1). The presentation of pNETs varies widely, with over 60 % having malignant distant disease at the time of initial diagnosis involving the liver or other distant sites. Functioning pNETs represent approximately 10 % of all pNETs, secrete a variety of peptide hormones, and are responsible for several clinical syndromes caused by profound hormonal derangement. Surgery remains the cornerstone of therapy and the only curative approach. It should be pursued for localized disease and for metastatic lesions amenable to resection. Multimodality therapies, including liver-directed therapies and medical therapy, are gaining increasing favor in the treatment of advanced pNETs. Their utility is multifold and spans from ameliorating symptoms of hormonal excess (functional pNETs) to controlling the local and systemic disease burden (non-functional pNETs). The recent introduction of target molecular therapy has promising results especially for the treatment of progressive well-differentiated G1/G2 tumor. In this review, we summarize the current knowledge and give an update on recent advancements made in the therapeutic strategies for pNETs.

(18)F-FDG-PET/CT findings in pancreatic metastasis

PURPOSE

This study aimed to evaluate the fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) findings and pattern of FDG uptake in pancreatic metastases.

MATERIALS AND METHODS

A total of 19 consecutive patients (26 lesions) with histologically or clinically confirmed pancreatic metastases who had undergone (18)F-FDG-PET/CT were enrolled in this retrospective study. Among the 19 patients, 14 patients underwent abdominal contrast-enhanced CT (ceCT). The location, size and FDG uptake patterns of the pancreatic lesions were recorded. Metabolic activity by means of maximum standardised uptake value (SUVmax) was measured by drawing regions of interest at the site of pancreatic lesions. Twenty pancreatic cancer patients were included in this study as comparative data analysis. The difference of SUVmax between pancreatic metastases and primary pancreatic cancer were compared using the Mann-Whitney U test. P < 0.05 was considered significant.

RESULTS

Three different patterns of FDG uptake could be distinguished in the pancreatic metastatic lesions, including focal nodule or mass, multiple foci and segmental lesion with high FDG uptake. The average SUVmax in pancreatic metastases was 7.8 ± 6.9 versus 7.4 ± 3.9 in primary pancreatic cancer (P = 0.987 > 0.05). Four intrapancreatic isodense nodules in three patients were undetected on ceCT.

CONCLUSION

The described patterns of FDG uptake findings may be helpful for a better characterisation of pancreatic metastases although semiquantitative analysis using SUVmax could not be used as a criterion for differentiating pancreatic metastases from primary pancreatic cancer. FDG-PET/CT has also an advantage in detecting unsuspected pancreatic metastases which cannot be detected by ceCT imaging. Thus, it is a useful adjunct to the described features on CT.

THERANOSTICS-clinical aimshots in surgical warfare against well-differentiated neuroendocrine neoplasms

Targeted, personalized or molecular medicine all imply maximal treatment with minimal side effects and requires definition and detection of molecular targets prior to therapy. THERANOSTICS in nuclear medicine utilizes the same vector with distinct radionuclides for diagnosis and treatment and has become innovative standard for the treatment of somatostatin receptor expressing neuroendocrine neoplasms.

Strengths and limitations of using 18fluorine-fluorodihydroxyphenylalanine PET/CT for congenital hyperinsulinism

¹⁸fluorine-fluorodihydroxyphenylalanine (FDOPA) PET/CT is currently the first-line imaging technique to distinguish between focal and diffuse forms of congenital hyperinsulinism (CHI) and to accurately localize focal forms. However, this technique has a number of limitations, mainly the very small size of focal forms or inversely a very large focal form mimicking a diffuse form, and misinterpretation of physiologic uptake masking hot spots or inversely mimicking focal forms. The other limitation is the limited availability of the radiopharmaceutical. FDOPA PET/CT has no recognized competitor to date among the available morphologic and functional imaging techniques. Other potential approaches using specific tracers for positron emission tomography (PET) are discussed, using radiopharmaceuticals specific for β cell mass or targeting somatostatin receptors. These radiopharmaceuticals can be labeled with gallium-68, a PET emitter readily available in PET centers equipped with 68Ge/68Ga generators.

Clinical correlations with (18)FDG PET scan patterns in solid pseudopapillary tumors of the pancreas: still a surgical enigma?

BACKGROUND

There are limited numbers of PET studies of solid pseudopapillary tumors (SPT) of the pancreas.

MATERIALS AND METHODS

We reviewed the medical records of 37 patients who underwent resection of pancreatic SPT and had been preoperatively evaluated by (18)F-FDG PET or PET/CT scan. Immunohistochemical analysis of glucose transporter-1 (GLUT-1) and hexokinase II (HK-II) was performed.

RESULTS

SPT could be categorized into five types according to the morphologic characteristics observed in PET images. Type I (hot FDG uptake in the entire tumor portion) was the most frequent (13, 34.2%), followed by type IV (focal uptake, 12, 31.6%), II (focal defect, 8, 21.1%), III (multiple and geographic uptake, 3, 7.9%), and V (total defective type, 1, 2.6%). The SUVmax in the solid portion of the SPT was 5.3 ± 4.1. The clinical pattern of FDG uptake in SPT was not associated with histopathologic features suggesting malignant potential. The SUVmax of SPT followed a pattern according to pattern of FDG uptake (R(2) = 0.203, p = 0.055), and was significantly associated with adjusted tumor volume (p = 0.001). GLUT-1 was not expressed in SPT, and only eight patients (12.3%) showed mild to moderate expression of HK-II, which was associated with the clinical pattern of SPT in PET images (p < 0.05).

CONCLUSION

SPT of the pancreas could be categorized according to the morphologic patterns observed in PET images. The clinical significance of FDG uptake, glucose metabolism, and clinical usefulness of PET scan in SPT need to be further investigated, and thus this tumor remains a surgical enigma.

Evaluation of neuroendocrine liver metastases: a comparison of dynamic contrast-enhanced magnetic resonance imaging and positron emission tomography/computed tomography

OBJECTIVES

The objective of this study was to evaluate the correlation between dynamic gadoxetic acid-enhanced magnetic resonance imaging parameters and specific uptake values (SUVs) derived from ¹⁸fluorodeoxyglucose (¹⁸F-FDG) and ⁶⁸Ga-DOTA-Tyr(3)-octreotate (⁶⁸Ga-DOTATATE) positron emission tomography/computed tomography (PET/CT) in patients with liver metastases of neuroendocrine neoplasms.

METHODS

A total of 42 patients with hepatic metastases of neuroendocrine neoplasms were prospectively enrolled and underwent both dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and PET/CT, using either ¹⁸F-FDG or ⁶⁸Ga-DOTATATE as tracer. The DCE-MRI was performed at 3 T with gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid acquiring 48 slices every 2.2 seconds for 5 minutes. Three regions of interest (ROIs) representing the liver background and up to 3 ROIs representing metastatic liver tissue were coregistered in the PET/CT and in the DCE-MRI data sets. For each patient, a dedicated dual-inlet, 2-compartment uptake model was fitted to the enhancement curves of DCE-MRI ROIs and perfusion parameters were calculated. Lesion-to-background ratios of SUVs were correlated with corresponding lesion-to-background ratios of the perfusion parameters arterial plasma flow, venous plasma flow, total plasma flow, extracellular mean transit time, extracellular volume, arterial flow fraction, intracellular uptake rate, and hepatic uptake fraction using the Spearman coefficient.

RESULTS

Whereas the lesion-to-background ratios of arterial plasma flow and arterial flow fraction of liver metastases correlated negatively with the lesion-to-background ratios of SUV(mean) derived from ⁶⁸Ga-DOTATATE PET/CT (r = -0.54, P < 0.001; r = -0.39, P < 0.001, respectively), they correlated positively with the lesion-to-background ratios of SUV(mean) derived from ¹⁸F-FDG-PET/CT (r = 0.51, P < 0.05; r = 0.68, P < 0.01, respectively). The lesion-to-background ratios of the DCE-MRI parameters extracellular mean transit time and extracellular volume correlated very weakly with the lesion-to-background ratios of SUV(mean) from ⁶⁸Ga-DOTATATE PET/CT, whereas venous plasma flow, total plasma flow, hepatic uptake fraction, and intracellular uptake rate showed no correlation between DCE-MRI and PET/CT.

CONCLUSIONS

Both ⁶⁸Ga-DOTATATE and ¹⁸fluorodeoxyglucose PET/CT partially correlate with MRI perfusion parameters from the dual-inlet, 2-compartment uptake model. The results indicate that the paired imaging methods deliver complementary functional information.

Successful treatment of metastasized pancreatic vasoactive intestinal polypeptide-secreting tumor unresponsive to high-dose octreotide by peptide receptor radionuclide therapy using 90Y DOTATATE

We report a successful treatment of a patient with heavily metastasized pancreatic vasoactive intestinal polypeptide-secreting tumor, which was unresponsive to high doses of octreotide analog using peptide receptor radionuclide therapy applying a radiolabeled somatostatin analog. After the peptide receptor radionuclide therapy, there was a decrease in vasoactive intestinal polypeptide levels, a significant reduction in somatostatin receptor expression and in molecular tumor volume on 68Ga DOTANOC PET/CT scan, and a complete long-term resolution of symptoms of the patient.

GEP-NETS update: functional localisation and scintigraphy in neuroendocrine tumours of the gastrointestinal tract and pancreas (GEP-NETs)

For patients with neuroendocrine tumours (NETs) of the gastrointestinal tract and pancreas (GEP) (GEP-NETs), excellent care should ideally be provided by a multidisciplinary team of skilled health care professionals. In these patients, a combination of nuclear medicine imaging and conventional radiological imaging techniques is usually mandatory for primary tumour visualisation, tumour staging and evaluation of treatment. In specific cases, as in patients with occult insulinomas, sampling procedures can provide a clue as to where to localise the insulin-hypersecreting pancreatic NETs. Recent developments in these fields have led to an increase in the detection rate of primary GEP-NETs and their metastatic deposits. Radiopharmaceuticals targeted at specific tumour cell properties and processes can be used to provide sensitive and specific whole-body imaging. Functional imaging also allows for patient selection for receptor-based therapies and prediction of the efficacy of such therapies. Positron emission tomography/computed tomography (CT) and single-photon emission CT/CT are used to map functional images with anatomical localisations. As a result, tumour imaging and tumour follow-up strategies can be optimised for every individual GEP-NET patient. In some cases, functional imaging might give indications with regard to future tumour behaviour and prognosis.

Diagnostic accuracy of dynamic gadoxetic-acid-enhanced MRI and PET/CT compared in patients with liver metastases from neuroendocrine neoplasms

PURPOSE

To evaluate the diagnostic accuracy of dynamic-contrast-enhanced (DCE) MRI in comparison to both (18)F-FDG- and (68)Ga-DOTATATE-PET/CT in patients with liver metastases of neuroendocrine neoplasms (NEN).

MATERIALS AND METHODS

Thirty-two patients with hepatic metastases from NEN were examined both in DCE-MRI and positron emission tomography/computed tomography (PET/CT), using either (18)F-fluorodeoxyglucose ((18)F-FDG) or (68)Ga-DOTATATE as tracer. DCE-MRI was performed at 3 Tesla with Gd-EOB-DTPA acquiring 48 slices every 2.2 s for 5 min. Three regions of interest (ROIs) representing liver background and liver metastases were defined in fat-saturated T1w three-dimensional GRE MRI sequences in the hepatobiliary phase. Corresponding ROIs were then defined in the DCE-MRI- and in the PET/CT-dataset. Area under the curve (AUC) was calculated for the differentiation between metastases and liver background for DCE-MRI and PET-CT parameters.

RESULTS

AUC was very high for SUVmean (mean standardized uptake value) derived from (68)Ga-DOTATATE- (AUC = 0.966), and (18)F-FDG-PET/CT (AUC = 0.989). For DCE-MRI parameters, arterial flow fraction and intracellular uptake fraction showed the highest AUCs (AUC = 0.826, AUC = 0.819, respectively). The combination of those two had an AUC of 0.949. The combination of DCE-MRI and PET-CT parameters resulted in the highest AUC.

CONCLUSION

Both PET/CT parameters and DCE-MRI perfusion parameters show a high diagnostic accuracy in the distinction between liver metastases and liver tissue. Our data suggest that both modalities provide complementary information.

Relevance of PET for pretherapeutic prediction of doses in peptide receptor radionuclide therapy

Personalized dosimetry in radionuclide therapy has gained much attention in recent years. This attention has also an impact on peptide receptor radionuclide therapy (PRRT). This article reviews the PET-based imaging techniques that can be used for pretherapeutic prediction of doses in PRRT. More specifically the usage of (86)Y, (90)Y, (68)Ga, and (44)Sc are discussed: their characteristics for PET acquisition, the available peptides for labeling, the specifics of the imaging protocols, and the experiences gained from phantom and clinical studies. These techniques are evaluated with regard to their usefulness for dosimetry predictions in PRRT, and future perspectives are discussed.

Comparison of abdominal MRI with diffusion-weighted imaging to 68Ga-DOTATATE PET/CT in detection of neuroendocrine tumors of the pancreas

PURPOSE

The aim of the study was to evaluate contrast-enhanced MRI, diffusion-weighted MRI (DW MRI), and (68)Ga-DOTATATE positron emission tomography (PET)/CT in the detection of intermediate to well-differentiated neuroendocrine tumors (NET) of the pancreas.

METHODS

Eighteen patients with pathologically proven pancreatic NET who underwent MRI including DW MRI and PET/CT within 6 weeks of each other were included in this retrospective study. Two radiologists evaluated T2-weighted (T2w), T2w + DW MRI, T2w + contrast-enhanced T1-weighted (CE T1w) MR images, and PET/CT for NET detection. The sensitivity and level of diagnostic confidence were compared among modalities using McNemar's test and a Wilcoxon signed rank test. Apparent diffusion coefficients (ADC) of pancreatic NETs and normal pancreatic tissue were compared with Student's t test.

RESULTS

Of the NETs, 8/23 (34.8 %) and 9/23 (39.1 %) were detected on T2w images by observers 1 and 2, respectively. Detection rates improved significantly by combining T2w images with DW MRI (observer 1: 14/23 = 61 %; observer 2: 15/23 = 65.2 %; p < 0.05) or CE T1w images (observer 1: 14/23 = 61 %; observer 2: 15/23 = 65.2 %; p < 0.05). Detection rates of pancreatic NET with PET/CT (both observers: 23/23 = 100 %) were statistically significantly higher than with MRI (p < 0.05). The mean ADC value of NET (1.02 ± 0.26 × 10(-3) mm(2)/s) was statistically significantly lower than that of normal pancreatic tissue (1.48 ± 0.39 × 10(-3) mm(2)/s).

CONCLUSION

DW MRI is a valuable adjunct to T2w imaging and comparable to CE T1w imaging in pancreatic NET detection, quantitatively differentiating between NET and normal pancreatic tissue with ADC measurements. (68)Ga-DOTATATE PET/CT is more sensitive than MRI in the detection of pancreatic NET.