A review of the current clinical trials for gastroenteropancreatic neuroendocrine tumours

Potent suppression of neuroendocrine tumors and gastrointestinal cancers by CDH17CAR T cells without toxicity to normal tissues

Gastrointestinal cancers (GICs) and neuroendocrine tumors (NETs) are often refractory to therapy after metastasis. Adoptive cell therapy using chimeric antigen receptor (CAR) T cells, though remarkably efficacious for treating leukemia, is yet to be developed for solid tumors such as GICs and NETs. Here we isolated a llama-derived nanobody, VHH1, and found that it bound cell surface adhesion protein CDH17 upregulated in GICs and NETs. VHH1-CAR T cells (CDH17CARTs) killed both human and mouse tumor cells in a CDH17-dependent manner. CDH17CARTs eradicated CDH17-expressing NETs and gastric, pancreatic and colorectal cancers in either tumor xenograft or autochthonous mouse models. Notably, CDH17CARTs do not attack normal intestinal epithelial cells, which also express CDH17, to cause toxicity, likely because CDH17 is localized only at the tight junction between normal intestinal epithelial cells. Thus, CDH17 represents a class of previously unappreciated tumor-associated antigens that is 'masked' in healthy tissues from attack by CAR T cells for developing safer cancer immunotherapy.

Clinical and Translational Research Challenges in Neuroendocrine Tumours

Neuroendocrine tumours (NETs) represent a range of neoplasms that may arise from any (neuro)endocrine cell situated in any part of the human body. As any other rare diseases, NETs face several difficulties in relation to research. This review will describe some of the main challenges and proposed solutions faced by researchers with expertise in rare malignancies. Some of the most common challenges in clinical and translational research are enumerated in this review, covering aspects from clinical, translational and basic research. NETs being a heterogeneous group of diseases and a limited sample size of clinical and translational research projects are the main challenges. Challenges with NETs lay over the disparities between healthcare models to tackle rare diseases. NETs add an extra layer of complexity due to a numerous group of different entities. Prospective real-world data trials are an opportunity for rare cancers with the revolution of electronic health technologies. This review explores potential solutions to these challenges that could be useful not only to the NET community but also to other rare tumours researchers.

BRD4 inhibitor IBET upregulates p27kip/cip protein stability in neuroendocrine tumor cells

The prevalence of neuroendocrine tumors (NETs) has recently been increasing. Although various drugs such as Octreotide and its analogs show certain efficacy, NETs in many patients progress and metastasize. It is desirable to develop new interventions to improve the therapy. Here we show that human neuroendocrine tumor BON cells are resistant to several drugs commonly used for NET therapy, including Octreotide that activates somatostatin receptor-induced anti-proliferation, and Capecitabine and Temozolimide that damage DNA. In contrast, an inhibitor (IBET) to an epigenetic regulator, Brd4 that binds acetylated histones and upregulates transcription of multiple genes including protooncogene c-Myc, potently inhibited the NET cells. We found that IBET increased the protein levels of cyclin-dependent kinase (CDK) inhibitor p27^kip/cip (or p27), but not its mRNA levels. Moreover, the p27 induction at protein level by IBET was at least partly through increasing the protein stability of p27. The increased protein stability of p27 likely resulted from IBET-mediated suppression of Skp2, an E3 ligase that can mediate p27 degradation by increasing its ubiquitinylation. These findings unravel a new mechanism whereby the IBET-induced repression of proliferation of neuroendocrine cells.

Pancreatic endocrine neoplasms: a current update on genetics and imaging

Pancreatic endocrine neoplasms are rare pancreatic tumours that may occur sporadically or as part of inherited syndromes such as multiple endocrine neoplasia-1 syndrome, von Recklinghausen disease, von Hippel-Lindau syndrome and tuberous sclerosis complex. Recent advances in the genetics and pathology of hereditary syndromes have provided valuable insights into the pathophysiology and biology of sporadic pancreatic endocrine neoplasms. Evolving molecular data on the biology of these neoplasms have the potential for diagnostic, therapeutic and prognostic use.

Antitumor effects of somatostatin analogs in neuroendocrine tumors

BACKGROUND

For decades, somatostatin analogs (including octreotide and lanreotide) have been indicated for relief of the symptoms of flushing, diarrhea, and wheezing associated with secretory neuroendocrine tumors (NETs). Recently, it has been suggested that somatostatin analogs may provide direct and indirect antitumor effects in secretory and nonsecretory NETs in addition to symptom control in secretory NETs.

METHODS

A systematic review of MEDLINE was conducted to identify studies that investigated the antitumor effects of octreotide or lanreotide for patients with NETs. Additional studies not published in the peer-reviewed literature were identified by searching online abstracts. Results. In all, 17 octreotide trials and 11 lanreotide trials that included antitumor effects were identified. Partial response rates were between 0% and 31%, and stable disease rates were between 15% and 89%. Octreotide was the only somatostatin analog for which results of a phase III, randomized, placebo-controlled clinical trial that investigated antitumor effects were published. After 6 months of treatment in this randomized phase III trial, stable disease was observed in 67% of patients (hazard ratio for time to disease progression: 0.34; 95% confidence interval: 0.20-0.59; p = .000072).

CONCLUSIONS

In addition to symptom control for NETs, the data support an antitumor effect of somatostatin analogs and suggest that they may slow tumor growth. Long-acting repeatable octreotide has been shown to have an antitumor effect in a randomized phase III trial in midgut NETs, whereas results are pending in a corresponding controlled trial with lanreotide for patients with intestinal and pancreatic primary NETs.

Contemporary management of nonfunctioning pancreatic neuroendocrine tumors

BACKGROUND

This article reviews the current literature and recommendations pertaining to the management of nonfunctioning pancreatic neuroendocrine tumors.

DISCUSSION

In recent years the detection of nonfunctioning pancreatic neuroendocrine tumors has increased coincident with the increased use of cross-sectional imaging and is now thought to represent 2-10% of all pancreatic tumors. Improved understanding of the biology and behavior of these heterogeneous tumors is needed to guide therapy. The present review discusses diagnostics, therapeutics including emerging molecular analytics, and surveillance recommendations.

Gastroenteropancreatic neuroendocrine tumors: new insights in the diagnosis and therapy

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are relatively rare and heterogenous malignancies. Recent advances in histopathological classification according to the anatomical site of origin, proliferation rate, and extend of the disease have created a valid and powerful tool for the prognostic stratification of GEP-NETs. Chromogranin A is still the best available marker used for the biochemical confirmation of these tumors, but new more sensitive markers are urgently required. Although scintigraphy with (111)In-octreotide has widely been applied for the localization and staging of GEP-NETs, newer imaging modalities based on the functional characteristics of these tumors are evolving aiming not only to facilitate the diagnosis but also prognosis and evaluation of treatment. Somatostatin receptors are the primary therapeutic targets through somatostatin analogs and peptide receptor radionuclide therapy (PRRT) producing symptomatic, biochemical and to a lesser extent antiproliferative effects. Due to the relatively limited and erratic response to chemotherapy, new molecular targeted therapies exploiting some of the biological properties of GEP-NETs such as increased vascularity and inhibition of pathways involved in downstream signal transduction have evolved. Some of these therapies, the mTOR inhibitor everolimus and the tyrosine kinase inhibitor sunitinib, have been recently validated in phase III studies producing practice changing outcomes. In addition, two oral chemotherapeutic agents temozolomide and capecitabine, show promising effects and may replace streptozotocin-based regimens whereas combination therapies with the angiogenesis inhibitor bevacizumab are being investigated. Although progression free survival is used as a feasible primary end point due to the long survival of patients even in the presence of extensive disease prolongation of overall survival following the introduction of new therapies needs to be established.

Pancreatic endocrine tumours: mutational and immunohistochemical survey of protein kinases reveals alterations in targetable kinases in cancer cell lines and rare primaries

BACKGROUND

Kinases represent potential therapeutic targets in pancreatic endocrine tumours (PETs).

PATIENTS AND METHODS

Thirty-five kinase genes were sequenced in 36 primary PETs and three PET cell lines: (i) 4 receptor tyrosine kinases (RTK), epithelial growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), tyrosine-protein kinase KIT (KIT), platelet-derived growth factor receptor alpha (PDGFRalpha); (ii) 6 belonging to the Akt/mTOR pathway; and (iii) 25 frequently mutated in cancers. The immunohistochemical expression of the four RTKs and the copy number of EGFR and HER2 were assessed in 140 PETs.

RESULTS

Somatic mutations were found in KIT in one and ATM in two primary neoplasms. Among 140 PETs, EGFR was immunopositive in 18 (13%), HER2 in 3 (2%), KIT in 16 (11%), and PDGFRalpha in 135 (96%). HER2 amplification was found in 2/130 (1.5%) PETs. KIT membrane immunostaining was significantly associated with tumour aggressiveness and shorter patient survival. PET cell lines QGP1, CM and BON harboured mutations in FGFR3, FLT1/VEGFR1 and PIK3CA, respectively.

CONCLUSIONS

Only rare PET cases, harbouring either HER2 amplification or KIT mutation, might benefit from targeted drugs. KIT membrane expression deserves further attention as a prognostic marker. ATM mutation is involved in a proportion of PET. The finding of specific mutations in PET cell lines renders these models useful for preclinical studies involving pathway-specific therapies.

Pancreatic endocrine tumors with major vascular abutment, involvement, or encasement and indication for resection

BACKGROUND

Surgery for pancreatic endocrine tumors (PETs) with blood vessel involvement is controversial.

HYPOTHESIS

Resection of PETs with major blood vessel involvement can be beneficial.

DESIGN

The combined databases of the National Institutes of Health and Stanford University hospitals were queried.

MAIN OUTCOME MEASURES

Operation, pathologic condition, complications, and disease-free and overall survival.

RESULTS

Of 273 patients with PETs, 46 (17%) had preoperative computed tomography evidence of major vascular involvement. The mean size for the primary PET was 5.0 cm. The involved major vessel was as follows: portal vein (n = 20), superior mesenteric vein or superior mesenteric artery (n = 16), inferior vena cava (n = 4), splenic vein (n = 4), and heart (n = 2). Forty-two of 46 patients had a PET removed: 12 (27%) primary only, 30 (68%) with lymph nodes, and 18 (41%) with liver metastases. PETs were removed by either enucleation (n = 7) or resection (n = 35). Resections included distal or subtotal pancreatectomy in 23, Whipple in 10, and total in 2. Eighteen patients had concomitant liver resection: 10 wedge resection and 8 anatomic resections. Nine patients had vascular reconstruction: each had reconstruction of the superior mesenteric vein and portal vein, and 1 had concomitant reconstruction of the superior mesenteric artery. There were no deaths, but 12 patients had complications. Eighteen patients (41%) were immediately disease free, and 5 recurred with follow-up, leaving 13 (30%) disease-free long term. The 10-year overall survival was 60%. Functional tumors were associated with a better overall survival (P < .001), and liver metastases decreased overall survival (P < .001).

CONCLUSION

These findings suggest that surgical resection of PETs with vascular abutment/invasion and nodal or distant metastases is indicated.

Angiogenic markers endoglin and vascular endothelial growth factor in gastroenteropancreatic neuroendocrine tumors

AIM: To investigate the expression and potential prognostic role of vascular endothelial growth factor (VEGF) and endoglin in gastroenteropancreatic neuroendocrine tumors (GEP-NETs).

METHODS: Microvessel density (MVD) in GEP-NETs was evaluated using endoglin and CD31 immunohistochemistry. In addition, tissue levels of endoglin and VEGF were determined in homogenates by ELISA.

RESULTS: Endoglin was highly expressed on tumor endothelial cells. CD31 MVD in GEP-NETs was significantly higher compared to endoglin MVD (P < 0.01). Two- to four-fold higher tissue levels of endoglin and VEGF were seen in tumors compared to associated normal tissue. This increased endoglin tissue expression in tumors was significantly related to tumor size (P < 0.01), presence of metastases (P = 0.04), and a more advanced tumor stage (P = 0.02), whereas expression of VEGF was not.

CONCLUSION: We suggest that endoglin is a potential marker to indicate and predict metastases, which might be useful in the post-resection therapeutic approach of patients with GEP-NETs.

Novel anticancer agents in clinical trials for well-differentiated neuroendocrine tumors

Neuroendocrine tumors (NETs) are rare malignancies that arise from endocrine cells located in various anatomic locations, with a dramatic increase in incidence during the last 30 years. Limited therapeutic options are currently available for patients with advanced well-differentiated NETs, including carcinoids and pancreatic NETs. Streptozotocin-based chemotherapy and somatostatin analogues are drugs that are currently used for the treatment of progressive metastatic NETs. Recently, sunitinib demonstrating efficacy in pancreatic islet cell carcinomas has opened a new avenue for the treatment of NETs, and further trials shall be considered in NET types such as carcinoids, poorly differentiated neuroendocrine carcinomas, and several other endocrine tumors that depend on vascular endothelial growth factor (VEGF)/VEGF receptor for angiogenesis. In addition, drugs with distinct mechanisms of action, such as mammalian target of rapamycin inhibitors, currently investigated in phase 3 trials, may also supply novel options to control tumor growth and metastasis. Although acknowledged as rare tumors, recent data demonstrated the feasibility of large randomized trials in this disease. Furthermore, data from large trials also showed the importance of selecting an appropriate patient population when designing randomized studies. This review focuses on novel therapeutic approaches in the treatment of well-differentiated NETs. Based on recent data, novel strategies may now be designed using those anticancer agents to optimize the current treatment of patients with NETs.

Surgical resection and multidisciplinary care for primary and metastatic pancreatic islet cell carcinomas

INTRODUCTION

The role of multidisciplinary management of islet cell cancers (ICC) has not been fully investigated in a population-based setting.

METHODS

The Los Angeles County Cancer Surveillance Program was assessed for patients with ICC between the years 1982 to 2006. Patients were stratified by treatment received and clinicopathologic characteristics and survival were compared.

RESULTS

We identified 236 patients with ICC; 86 patients underwent curative-intent surgery with median survival for local, regional, and distant disease of 17.3, 12.2, and 4.0 years, respectively. In comparison, 102 patients underwent medical management alone; survival was significantly shorter when compared to the surgical cohort for local, regional, and distant disease (p < 0.05). To determine whether adjuvant chemotherapy was associated with improved survival, we compared patients who underwent surgery alone compared to patients who underwent surgery followed by adjuvant chemotherapy. Although patients with metastatic disease had 3-year longer survival with adjuvant chemotherapy, these improvements in survival were not statistically significant.

CONCLUSION

Surgical resection was associated with improved survival compared to medical management for any extent of disease in patients with ICC. Furthermore, adjuvant chemotherapy was not associated with survival but does warrant further examination in patients with metastatic disease.

Recent trends in the treatment of well-differentiated endocrine carcinoma of the small bowel

Well-differentiated endocrine carcinomas of the small bowel are fairly rare neoplasms that present many clinical challenges. They secrete peptides and neuroamines that may cause carcinoid syndrome. However, many are clinically silent until late presentation with major effects. Initial treatment aims to control carcinoid syndrome with somatostatin analogs. Even if there is metastatic spread, surgical resection of the primitive tumor should be discussed in cases of retractile mesenteritis, small bowel ischemia or subocclusive syndrome in order to avoid any acute complication, in particular at the beginning of somatostatin analog treatment. The choice of treatment depends on the symptoms, general health of the patient, tumor burden, degree of uptake of radionuclide, histological features of the tumor, and tumor growth. Management strategies include surgery for cure (which is rarely achieved) or for cytoreduction, radiological interventions (transarterial embolization or radiofrequency ablation), and chemotherapy (interferon and somatostatin analogs). New biological agent and radionuclide targeted therapies are under investigation. Diffuse and non-evolving lesions should also be simply monitored. Finally, it has to be emphasized that it is of the utmost importance to enroll these patients with a rare disease in prospective clinical trials assessing new therapeutic strategies.

The potential role of sunitinib in gastrointestinal cancers other than GIST

Gastrointestinal tumors are the most frequent and lethal malignancies worldwide. The deeper knowledge in molecular biology mechanisms involved in carcinogenesis has allowed the design of new targeted drugs mainly directed against the epidermal growth factor receptor (EGFR), the vascular endothelial growth factor (VEGF) and its receptors (VEGFRs). Sunitinib is an oral multitargeted inhibitor of the VEGF, platelet-derived growth factor (PDGF), and c-KIT, among others, tyrosine kinase receptors. Therefore, sunitinib acts in a dual mode as antiangiogenic agent and as antitumoral drug. The aim of this review is to gather the preclinical rationale behind the clinical use of sunitinib in gastrointestinal malignancies other than gastrointestinal stromal tumors (GIST) and to summarize the clinical data from phase I to III trials currently available.

Effects of somatostatin analogs on glucose homeostasis: a metaanalysis of acromegaly studies

BACKGROUND

Somatostatin analogs (SSA) may influence glucose metabolism, but the clinical relevance of this effect is uncertain because trials performed so far are limited in terms of number of patients and heterogeneity for length and type of follow-up.

PURPOSE

The purpose of the study was to assess, via the metaanalysis of acromegaly studies, the clinical impact of SSA on glucose metabolism. The outcomes analyzed were fasting plasma glucose, fasting plasma insulin, hemoglobin A(1c), and plasma glucose concentrations during oral glucose tolerance test.

STUDY SELECTION

Eligibility criteria were: 1) duration of SSA treatment of at least 3 wk; 2) available numerical data for at least one of the four biochemical outcomes investigated; 3) measurement of the outcomes before and after SSA treatment; and 4) no selection of acromegalic patients for their responsivity to SSA. After revision, only 31 studies fulfilled eligibility criteria and were therefore selected for data extraction and analysis.

DATA SYNTHESIS

SSA treatment was found to induce statistically significant decrease in fasting plasma insulin [effect size -0.45, 95% confidence interval (CI) from -0.58 to -0.32, P < 0.001], without any significant change of fasting plasma glucose (effect size +0.04, 95% CI from -0.07 to +0.15, P = 0.52) and hemoglobin A(1c) (effect size +0.11, 95% CI from -0.02 to +0.23, P = 0.09). Serum glucose values during the oral glucose tolerance test were shown to significantly change during SSA treatment (effect size +0.31, 95% CI from +0.17 to +0.45, P < 0.001), although with high inconsistency among trials.

CONCLUSIONS

Our data suggest that modifications of glucose homeostasis induced by SSA may have an overall minor clinical impact in acromegaly.

Gastrointestinal neuroendocrine tumors: pancreatic endocrine tumors

Pancreatic endocrine tumors (PETs) have long fascinated clinicians and investigators despite their relative rarity. Their clinical presentation varies depending on whether the tumor is functional or not, and also according to the specific hormonal syndrome produced. Tumors may be sporadic or inherited, but little is known about their molecular pathology, especially the sporadic forms. Chromogranin A appears to be the most useful serum marker for diagnosis, staging, and monitoring. Initially, therapy should be directed at the hormonal syndrome because this has the major initial impact on the patient's health. Most PETs are relatively indolent but ultimately malignant, except for insulinomas, which predominantly are benign. Surgery is the only modality that offers the possibility of cure, although it generally is noncurative in patients with Zollinger-Ellison syndrome or nonfunctional PETs with multiple endocrine neoplasia-type 1. Preoperative staging of disease extent is necessary to determine the likelihood of complete resection although debulking surgery often is believed to be useful in patients with unresectable tumors. Once metastatic, biotherapy is usually the first modality used because it generally is well tolerated. Systemic or regional therapies generally are reserved until symptoms occur or tumor growth is rapid. Recently, a number of newer agents, as well as receptor-directed radiotherapy, are being evaluated for patients with advanced disease. This review addresses a number of recent advances regarding the molecular pathology, diagnosis, localization, and management of PETs including discussion of peptide-receptor radionuclide therapy and other novel antitumor approaches. We conclude with a discussion of future directions and unsettled problems in the field.

Inhibition of proliferation of small intestinal and bronchopulmonary neuroendocrine cell lines by using peptide analogs targeting receptors

BACKGROUND

Currently, no consistently effective therapy is available to inhibit cell proliferation or metastasis of neuroendocrine tumor (NET) disease. The effects of 4 novel peptides were analyzed: a targeted cytotoxic analog of luteinizing hormone-releasing hormone (LH-RH) analog (AN-152), a targeted cytotoxic analog of somatostatin (AN-238), and 2 antagonists of growth hormone-releasing hormone (GH-RH) on 3 NET (carcinoid) cell lines that expressed respective peptide receptors.

METHODS

The effects of the compounds were evaluated on cell proliferation in vitro using MTT uptake and Ki67 expression, apoptosis (caspase 3 expression and activity), and cell cycle parameters (DNA distribution).

RESULTS

Proliferation of the LH-RH receptor-expressing lung NET, NCI-H720 line, was inhibited 2-fold by AN-152 containing doxorubicin compared with the chemotherapy alone (IC50 of 9.1 nM vs 24 nM). This was associated with a reduction in Ki67 transcript and an increase in both caspase 3 mRNA levels and activity. Proliferation of the GH-RH receptor expressing lung NET, NCI-H727 line, was inhibited by both GH-RH antagonists, the effects being mediated through changes in Ki67 expression, but not in caspase 3-mediated apoptosis. The small intestinal NET, KRJ-I line, was 8x more sensitive to inhibition by AN-238 than to 2-pyrolino-doxorubicin, reflected by increased caspase 3 transcript as well as activity. AN-238-mediated growth inhibition culminated in complete G1 arrest.

CONCLUSIONS

The data demonstrate GH-RH antagonists or peptide-linked antineoplastic agents such as AN-152 and AN-238 are effective inhibitors of NET proliferation in vitro. Because peptide receptors such as those for GH-RH, LH-RH, and SST subtypes are commonly expressed by NETs, the development of antineoplastic agents targeted to specific tumor receptors may provide a more efficacious strategy than systemic chemotherapeutic agents currently in use.

Medical treatment of gastrinomas

Gastrinomas are functional neuroendocrine tumors of the gastroenteropancreatic system. Surgery is first line treatment in gastrinomas, however often fails to be curative. This manuscript reviews current strategies of medical treatment of surgically non-curable gastrinoma. Symptomatic treatment with H(+)-K(+)-ATPase proton-pump inhibitors suppresses hypersecretion of gastric acid and substantially improves quality of life in patients with Zollinger-Ellison syndrome. Further medical therapy is only recommended in cases of progressive metastatic gastrinoma. In well differentiated neuroendocrine carcinoma (G1 and G2) a so-called biotherapy with somatostatin analogues exists as first-line and chemotherapy with streptocotozin plus doxorubicine/5-FU as second-line medical treatment option. In poorly differentiated neuroendocrine carcinoma (G3) chemotherapy with etoposide plus cisplatin is possible. Prospective future therapeutic strategies may include treatment with novel somatostatin analogues as well as angiogenesis inhibitors and kinase inhibitors targeting tumor-specific signaling cascades.

Functional MRI evaluation of tumor response in patients with neuroendocrine hepatic metastasis treated with transcatheter arterial chemoembolization

OBJECTIVE

The purpose of this study was to evaluate contrast-enhanced and diffusion-weighted MRI changes in neuroendocrine tumors treated with transcatheter arterial chemoembolization (TACE).

MATERIALS AND METHODS

Sixty-six targeted lesions in 26 patients (18 men, eight women; mean age, 57 years) with hepatic metastasis of neuroendocrine tumors treated with TACE were retrospectively analyzed. MRI studies were performed before and after TACE. Imaging features included tumor size, percentage of enhancement in the arterial and portal venous phases, and diffusion-weighted imaging apparent diffusion coefficients (ADCs) of the tumor, liver, and spleen. Tumor response to treatment was recorded according to World Health Organization criteria and Response Evaluation Criteria in Solid Tumors. Liver function tests were performed, and clinical performance was assessed before and after treatment. Statistical analysis included paired Student's t tests and Kaplan-Meier survival curves.

RESULTS

Mean tumor size and percentage enhancement in the arterial and portal venous phases decreased significantly after treatment (p < 0.0001). The tumor ADC increased from 1.51 x 10(-3) mm2/s before treatment to 1.79 x 10(-3) mm2/s after treatment (p < 0.0001), but the ADCs for the liver and spleen remained unchanged. Despite the change in tumor size, no patient in this cohort achieved complete response according to World Health Organization criteria and Response Evaluation Criteria in Solid Tumors. Partial response was achieved in only 27% and 23% of the patients according to the respective criteria. Results of liver function tests and performance status also remained unchanged. The mean survival period for all patients was 78 months.

CONCLUSION

Contrast-enhanced and diffusion-weighted imaging showed significant changes after TACE of neuroendocrine tumors and can be used to assess response of targeted tumors.

Current medical treatment of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (NETs) consist of a wide group of neoplasms, with different biological behaviors in terms of aggressiveness and hormone production. In the last two decades, significant progress has been observed in our understanding of their biology, diagnosis and treatment. Surgery remains to be the only curative approach, but unfortunately the diagnosis is often delayed due to the slow growth of these tumors and the difficulty in identifying the symptoms related to the tumor-released hormones. In addition to surgery, other approaches to control the disease are biological therapy consisting of somatostatin analogs and interferon (IFN), systemic chemotherapy, radioligand therapy and local therapy with chemoembolization. Several newer cytotoxic agents, including irinotecan, gemcitabine, taxanes, oxaliplatin, capecitabine and PS-341 have been studied in metastatic patients. Considering the high vascularity of these tumors, antiangiogenic agents like endostatin and thalidomide have also been evaluated in advanced NETs. Although these agents seem to have potential activity in NETs and may increase progression free survival, none of these currently available medical therapeutic options are curative. While more efficient novel strategies are to be developed, the rationale use of the current therapeutic options may improve quality of life, control the symptoms related to the hypersecretion of hormones and/or peptides, control tumor proliferation and prolong survival in patients suffering from NETs.