Gastroenteropancreatic neuroendocrine tumours (GEP-NET) - Imaging and staging

The utility of 68Ga-DOTATATE positron-emission tomography/computed tomography in the diagnosis, management, follow-up and prognosis of neuroendocrine tumors

Neuroendocrine tumors (NETs) are rare neoplasms that emerge mainly from the GI tract, pancreas and respiratory tract. The incidence of NETs has increased more than sixfold in the last decades. NETs typically express somatostatin receptors on their cell surface, which can be targeted by 'cold' somatostatin analogs for therapy or by 'hot' radiolabeled somatostatin analogs for tumor localization and treatment. 68-Gallium-DOTA peptides (DOTATATE, DOTATOC, DOTANOC) positron emission tomography/computed tomography is a highly accurate imaging modality for NETs that has been found to be more sensitive for NET detection than other imaging modalities. In the current review, we will discuss the clinical utility of 68-Gallium-DOTATATE positron emission tomography/computed tomography for the diagnosis and management of patients with NETs.

Predictive Factors for Lymph Node Metastasis and Prognostic Factors for Survival in Rectal Neuroendocrine Tumors

INTRODUCTION

Neuroendocrine tumors have malignant potential, and lymph node metastasis can occur. This study aimed to identify predictive factors of lymph node metastasis and prognostic factors for survival in rectal neuroendocrine tumors.

METHODS

Sixty-four patients underwent endoscopic or surgical treatment for rectal NET. The data on these patients were collected in our database prospectively and reviewed retrospectively.

RESULTS

Transanal excision was performed in 28 (43.8%) patients, endoscopic mucosal resection or submucosal dissection was performed in 15 (23.4%) patients, and radical resection was performed in 21 (31.8%) patients. Lymph node and distant metastasis was present in 16 (25.0%) and fir (7.8%) patients. The significant risk factors for lymph node metastasis identified in the multivariable analyses were tumor size (≥ 2 cm, p = 0.003) and tumor grade (G2, p < 0.001; G3, p = 0.008). In patients with a tumor smaller than 2 cm, the risk factors for lymph node metastasis included the tumor grade, mitosis count, and Ki-67 index. The median follow-up period was 30.0 months, and recurrence developed in four (6.8%) patients. The significant prognostic factors for survival included tumor size, T stage, lymph node metastasis, and tumor grade.

CONCLUSION

Tumor grade combined with tumor size is an important predictive factor for lymph node metastasis and could serve as a prognostic factor for survival outcomes.

Surgical Therapy of Sporadic Pancreatic Neuroendocrine Neoplasias G1/G2

Background

Pancreatic neuroendocrine neoplasias (pNENs) are uncommon but fascinating tumors with an annual incidence of 1 per 100,000 people. pNENs present either as functional tumors, causing specific hormonal syndromes like Zollinger-Ellison syndrome (ZES) or organic hyperinsulinism, or as non-functional pancreatic tumors (NF-pNENs). The natural history of pNENs is highly variable. 90% of all insulinomas or small NF- pNENs are readily curable by surgical resection. Most other functional and late detected NF-pNENs have a less favorable chance for cure.

Methods

A systematic review of the literature was performed to identify the current state of the art with regard to the key issues of surgery in pNEN G1/G2.

Results

This article provides a comprehensive review of the current literature addressing the current challenges in pNEN surgery.

Conclusion

Patients with completely resected tumors generally have a good prognosis, and an aggressive surgical approach combined with conservative treatment options in patients with advanced disease rarely provides cure but often results in long-term survival.

[Early endocrine neoplasia of the pancreas]

Pancreatic endocrine neoplasias (pNENs) are uncommon but fascinating tumors with a rising incidence. In accordance to its location, size and grading, the decision to operate the patient should always be made in an interdisciplinary approach. This article provides a comprehensive review of the current literature addressing the current challenges in pNEN surgery and shows that patients with completely resected small pNENs generally have an excellent prognosis, but also that surveillance may be a powerful tool.

The future: diagnostic and imaging advances in MEN1 therapeutic approaches and management strategies

Prospective randomized data are lacking, but current clinical expert guidelines recommend annual screening examinations, including laboratory assessments and various imaging modalities (e.g. CT, MRI, scintigraphy and EUS) for patients with multiple endocrine neoplasia type 1 (MEN1). Routine screening is proposed to detect and localize neuroendocrine manifestations as early as possible. The goal is timely intervention to improve quality of life and to increase life expectancy by preventing the development of life-threatening hormonal syndromes and/or metastatic disease. In recent years, some studies compared different and new imaging methods regarding their sensitivity and utility in MEN1 patients. This present article reviews the proposed diagnostic tools for MEN1 screening as well as potential future perspectives.

Somatostatin Receptor Antagonists for Imaging and Therapy

Somatostatin receptor (sstr) scintigraphy for imaging and sstr analogs for treatment have been used for more than 20 y. An important improvement in recent years was the introduction of peptide receptor radionuclide therapy with radiolabeled sstr agonists, such as [⁹⁰Y-DOTA⁰,Tyr³]octreotide or [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotide (⁹⁰Y- or ¹⁷⁷Lu-DOTATOC, respectively) and [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotate (¹⁷⁷Lu-DOTATATE). PET/CT with ⁶⁸Ga-labeled sstr agonists, such as ⁶⁸Ga-DOTATOC, ⁶⁸Ga-DOTATATE, and [⁶⁸Ga-DOTA,1-Nal³]octreotide (⁶⁸Ga-DOTANOC), plays an important role in staging and restaging neuroendocrine tumors. Most importantly, sstr scintigraphy and sstr PET/CT can distinguish patients who will qualify for and benefit from peptide receptor radionuclide therapy. This characteristic of sstr targeting is important because it allows a personalized treatment approach (theranostic approach). Until recently, it was thought that internalization of the radiolabeled agonist was mandatory for sstr-mediated imaging and therapy. It was Ginj et al. who proposed in 2006 the paradigm shift that radiolabeled sstr antagonists may perform better than agonists despite the lack of internalization. Despite the rather limited number of head-to-head comparisons of sstr antagonists and agonists, the superiority of sstr antagonists was demonstrated in several cases. From a small library of sstr antagonists, the analog JR11 (Cpa-c[d-Cys-Aph(Hor)-d-Aph(Cbm)-Lys-Thr-Cys]-d-Tyr-NH₂), an antagonist with selectivity for sstr subtype 2, showed the best overall characteristics for sstr subtype 2 targeting and was therefore selected for clinical translation. JR11 is under clinical development as a PET imaging agent when labeled with ⁶⁸Ga (⁶⁸Ga-NODAGA-JR11 or ⁶⁸Ga-OPS202) and as a therapeutic agent when labeled with ¹⁷⁷Lu (¹⁷⁷Lu-DOTA-JR11 or ¹⁷⁷Lu-OPS201). In this article, we discuss the development and current status of radiolabeled sstr antagonists. Evidence based on preclinical work, on quantitative in vivo autoradiography of human tumor slices, and on human data now supports a shift to sstr antagonists.

Diagnosing and Managing Carcinoid Heart Disease in Patients With Neuroendocrine Tumors: An Expert Statement

Carcinoid heart disease is a frequent occurrence in patients with carcinoid syndrome and is responsible for substantial morbidity and mortality. The pathophysiology of carcinoid heart disease is poorly understood; however, chronic exposure to excessive circulating serotonin is considered one of the most important contributing factors. Despite recognition, international consensus guidelines specifically addressing the diagnosis and management of carcinoid heart disease are lacking. Furthermore, there is considerable variation in multiple aspects of screening and management of the disease. The aim of these guidelines was to provide succinct, practical advice on the diagnosis and management of carcinoid heart disease as well as its surveillance. Recommendations and proposed algorithms for the investigation, screening, and management have been developed based on an evidence-based review of the published data and on the expert opinion of a multidisciplinary consensus panel consisting of neuroendocrine tumor experts, including oncologists, gastroenterologists, and endocrinologists, in conjunction with cardiologists and cardiothoracic surgeons.

Preclinical evaluation of PAC1 targeting with radiolabeled Maxadilan

There is an ongoing search for new tracers to optimize imaging of beta cell-derived tumors (insulinomas). The PAC1 receptor, expressed by insulinomas, can be used for targeting of these tumors. Here, we investigated whether radiolabeled maxadilan could be used for insulinoma imaging. Maxadilan was C- or N-terminally conjugated with DTPA (termed maxadilan-DPTA or DTPA-maxadilan respectively). BALB/c nude mice bearing subcutaneous INS-1 tumors were injected with either In-111-labeled maxadilan-DTPA or In-111-DTPA-maxadilan. Biodistribution studies were carried out at 1, 2 and 4 hours after injection and SPECT/CT imaging 1 and 4 hours after injection of maxadilan-DTPA-¹¹¹In. Radiolabeling of maxadilan-DTPA (680 MBq/nmol) was more efficient than of DTPA-maxadilan (55 MBq/nmol). Conjugation with DTPA slightly reduced receptor binding affinity in vitro: IC₅₀ values were 3.2, 21.0 and 21.0 nM for maxadilan, ^natIn-DTPA-maxadilan and maxadilan-DTPA-^natIn respectively. Upon i.v. injection maxadilan-DTPA-¹¹¹In accumulated specifically in INS-1 tumors (7.30 ± 1.87%ID/g) and in the pancreas (3.82 ± 0.22%ID/g). INS-1 tumors were clearly visualized by small animal SPECT/CT. In conclusion, this study showed that the high affinity of maxadilan to the PAC1 receptor was maintained after DTPA conjugation. Furthermore, radiolabeled maxadilan-DTPA accumulated specifically in INS-1 tumors and, therefore, may qualify as a useful tracer to image insulinomas.

Association between neuroendocrine tumors biomarkers and primary tumor site and disease type based on total 68Ga-DOTATATE-Avid tumor volume measurements

OBJECTIVE

To determine the association between neuroendocrine tumor (NET) biomarker levels and the extent of disease as assessed by ⁶⁸Ga DOTATATE PET/CT imaging.

DESIGN

A retrospective analysis of a prospective database of patients with NETs.

METHODS

Fasting plasma chromogranin A (CgA), neuron-specific enolase (NSE), gastrin, glucagon, vasoactive intestinal peptide (VIP) and pancreatic polypeptide (PP), and 24-h urinary 5-hydroxyindoleacetic acid (5-HIAA) levels were measured. Correlation between biomarkers and total ⁶⁸Ga-DOTATATE-avid tumor volume (TV) was analyzed.

RESULTS

The analysis included 232 patients. In patients with pancreatic NETs (n = 112), ⁶⁸Ga-DOTATATE TV correlated with CgA (r = 0.6, P = 0.001, Spearman). In patients with multiple endocrine neoplasia type 1 (n = 39), ⁶⁸Ga-DOTATATE TV correlated with glucagon (r = 0.5, P = 0.01) and PP levels (r = 0.5, P = 0.049). In patients with von Hippel-Lindau (n = 24), plasma VIP (r = 0.5, P = 0.02) and PP levels (r = 0.7, P < 0.001) correlated with ⁶⁸Ga-DOTATATE TV. In patients with small intestine NET (SINET, n = 74), ⁶⁸Ga-DOTATATE TV correlated with CgA (r = 0.5, P = 0.02) and 5-HIAA levels (r = 0.7, P < 0.001), with 5-HIAA ≥8.1 mg/24 h associated with metastatic disease with high positive (81.8%) and negative (85.7%) predictive values (P = 0.001). ⁶⁸Ga-DOTATATE TV in patients with NET of unknown primary (n = 16) and those with NET of other primary location (n = 30) correlated with 5-HIAA levels (r = 0.8, P = 0.002 and r = 0.7, P = 0.02 respectively).

CONCLUSIONS

Our data supports the use of specific NET biomarkers based on the site of the primary NET and the presence of hereditary syndrome-associated NET. High urinary 5-HIAA levels indicate the presence of metastatic disease in patients with SINET.

Molecular imaging in neuroendocrine tumors: recent advances, controversies, unresolved issues, and roles in management

PURPOSE OF REVIEW

The purpose is to review recent advances in molecular imaging of neuroendocrine tumors (NETs), discuss unresolved issues, and review how these advances are affecting clinical management.

RECENT FINDINGS

Molecular imaging of NETs underwent a number of important changes in the last few years, leading to some controversies, unresolved issues, and significant changes in clinical management. The most recent changes are reviewed in this article. Particularly important is the rapid replacement in somatostatin receptor scintigraphy of In-diethylenetriamine penta-acetic acid-single-photon emission computed tomography/computed tomography (CT) by Ga-fluorodopa(F-D)PA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-peptide-PET/CT imaging, which is now approved in many countries including the USA. Numerous studies in many different types of NETs demonstrate the greater sensitivity of Ga-DOTA-peptide PET/CT, its high specificity, and its impact on management. Other important developments in somatostatin receptor scintigraphy/molecular imaging include demonstrating the prognostic value of both Ga-DOTA-peptide PET/CT and F-fluoro-deoxyglucose PET/CT; how their use can be complementary; comparing the sensitivities and usefulness of Ga-DOTA-peptide PET/CT and F-FDOPA PET/CT; introducing new linkers and radiolabeled ligands such as Cu-DOTA-peptides with a long half-life, enhancing utility; and the introduction of somatostatin receptor antagonists which show enhanced uptake by NETs. In addition, novel ligands which interact with other receptors (GLP-1, bombesin, cholecystokinin, gastric inhibitory polpeptide, integrin, chemokines) are described, which show promise in the imaging of both NETs and other tumors.

SUMMARY

Molecular imaging is now required for all aspects of the management of patients with NETs. Its results are essential not only for the proper diagnostic management of the patient, but also for assessing whether the patient is a candidate for peptide receptor radionuclide therapy with Lu and also for providing prognostic value.

Guidelines for the management of neuroendocrine tumours by the Brazilian gastrointestinal tumour group

Neuroendocrine tumours are a heterogeneous group of diseases with a significant variety of diagnostic tests and treatment modalities. Guidelines were developed by North American and European groups to recommend their best management. However, local particularities and relativisms found worldwide led us to create Brazilian guidelines. Our consensus considered the best feasible strategies in an environment involving more limited resources. We believe that our recommendations may be extended to other countries with similar economic standards.

Molecular Imaging of Gastroenteropancreatic Neuroendocrine Tumors: Current Status and Future Directions

Through diagnostic imaging and peptide receptor radionuclide therapy, nuclear medicine has earned a major role in gastroenteropancreatic neuroendocrine tumors (GEP NETs). GEP NETs are diagnosed fortuitously or on the basis of symptoms or hormonal syndrome. The functional tumor characteristics shown by radionuclide imaging allow for more accurate staging and treatment selection. Tumor grade helps determine which tracer should be selected. In the past, ¹¹¹In-pentetreotide has been successful in well-differentiated (G1 and G2) tumors. However, PET/CT imaging with novel somatostatin analogs (e.g., ⁶⁸Ga-DOTATOC, ⁶⁸Ga-DOTATATE, ⁶⁸Ga-DOTANOC, and ⁶⁴Cu-DOTATATE) now offers improved sensitivity. ¹⁸F-fluorodihydroxyphenylalanine (¹⁸F-FDOPA) is another interesting radiopharmaceutical. ¹⁸F-FDOPA sensitivity is influenced by a tumor's capacity to take up, decarboxylate, and store amine precursors. ¹⁸F-FDOPA sensitivities are highest in ileal NETs and may also be helpful in insulinomas. A high uptake of ¹⁸F-FDG with a low uptake of somatostatin analog usually indicates poorly differentiated tumors (G3). Starting from these principles, this article discusses theranostic approaches to GEP NETs, taking into account both primary and metastatic lesions.

Treatment of symptomatic neuroendocrine tumor syndromes: recent advances and controversies

INTRODUCTION

Neuroendocrine tumors(NETs), once thought rare, are increasing in frequency in most countries and receiving increasing-attention. NETs present two-treatment problems. A proportion is aggressive and a proportion has a functional, hormone-excess-state(F-NET), each of which must be treated. Recently, there have been many advances, well-covered in reviews/consensus papers on imaging-NETs; new, novel anti-tumor treatments and understanding their pathogenesis. However, little attention has been paid to advances in the treatment of the hormone-excess-state. These advances are usually reported in case-series, and case-reports with few large studies. In this paper these advances are reviewed. Areas covered: Advances in the last 5-years are concentrated on, but a review of literature from the last 10-years was performed. PubMed and other databases (Cochrane, etc.) were searched for F-NET-syndromes including carcinoid-syndrome, as well as meeting-abstracts on NETs. All advances that controlled hormone-excess-states or facilitated-control were covered. These include new medical-therapies [serotonin-synthesis inhibitors(telotristat), Pasireotide, new agents for treating ACTHomas], increased dosing with conventional therapies (octreotide-LAR, Lanreotide-Autogel), mTor inhibitors(everolimus), Tyrosine-kinase inhibitors(sunitinib),cytoreductive surgery, liver-directed therapies (embolization, chemoembolization, radioembolization, RFA), peptide radio-receptor-therapy(PRRT) and ¹³¹I-MIBG, ablation of primary F-NETs. Expert opinion: Although many of the newer therapies controlling the hormone-excess-states in F-NETs are reported in relatively few patients, all the approaches show promise. Their description also generates some controversies/unresolved areas,such as the order of these new treatments, their longterm-efficacy, and effectiveness of combinations which may require large,controlled studies.