Sunitinib paves the way for targeted therapies in neuroendocrine tumors

Oncological management of advanced neuroendocrine tumours (Review)

The oncological principles of managing patients with gastroenteropancreatic neuroendocrine tumours (GEP-NETs) depends on a number of factors and requires a multidisciplinary approach. Recent data have provided additional therapeutic options, including biotherapy, traditional chemotherapy and novel targeted agents. Somatostatin analogues (SSAs) inhibit multiple cellular functions, including secretion, motility and proliferation. Interferon appears to act through several mechanisms, with antisecretory effects, immunomodulatory effects and antiproliferative functions, the latter inhibiting direct growth or attenuating angiogenesis. Opinions on when to commence chemotherapy for well differentiated GEP-NETs varies among experts. In previous years, reserving chemotherapy for patients with progressive disease (well differentiated, inoperable and/or metastatic GEP-NETs) was reasonably well argued for. Most well differentiated endocrine tumours are richly vascular and many express vascular endothelial growth factor (VEGF) receptors. In a xenograft model of a human carcinoid, treatment with an anti-VEGF monoclonal antibody was revealed to inhibit tumour growth and metastasis. As the role of angiogenesis and hypoxic-associated factors appears to be associated with tumour aggressiveness, strategies using agents which target angiogenesis have been developed. Mammalian target of rapamycin (mTOR) is a conserved serine-threonine kinase that regulates the cell cycle and metabolism in response to environmental factors. In addition, mTOR inhibition suppression was demonstrated to suppress NET growth. Each patient requires an individual approach to the choice of therapy, which should be selected depending on the severity of disease.

MicroRNA modulation combined with sunitinib as a novel therapeutic strategy for pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and mortal cancer, characterized by a set of known mutations, invasive features, and aberrant microRNA expression that have been associated with hallmark malignant properties of PDAC. The lack of effective PDAC treatment options prompted us to investigate whether microRNAs would constitute promising therapeutic targets toward the generation of a gene therapy approach with clinical significance for this disease. In this work, we show that the developed human serum albumin–1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine:cholesterol/anti-microRNA oligonucleotides (+/−) (4/1) nanosystem exhibits the ability to efficiently deliver anti-microRNA oligonucleotides targeting the overexpressed microRNAs miR-21, miR-221, miR-222, and miR-10 in PDCA cells, promoting an almost complete abolishment of microRNA expression. Silencing of these microRNAs resulted in a significant increase in the levels of their targets. Moreover, the combination of microRNA silencing, namely miR-21, with low amounts of the chemotherapeutic drug sunitinib resulted in a strong and synergistic antitumor effect, showing that this combined strategy could be of great importance for therapeutic application in PDAC.

Digestive neuroendocrine tumors (DNET): the era of targeted therapies

Neuroendocrine tumors (NETs) are a heterogeneous group of malignancies. Therapeutic options depend on location of the primitive tumor, its expandability, its hormonal symptoms and its differentiation. Though relatively rare, with an increasing incidence and a high prevalence digestive neuroendocrine tumors (DNETs) are ranked just behind colorectal cancer as the most common digestive cancers in developed countries. Three main therapeutic axes have been individualized in the field of well-differentiated DNETs (corresponding to grades 1 and 2 of new WHO classification 2010), firstly, antitumor activity of somatostatin analogs, particularly in slowly progressive metastatic DNETs with limited hepatic invasion, secondly, targeting angiogenesis in these hypervascular tumors and thirdly targeting the mTOR pathway involved in DNETs carcinogenesis. As a consequence of two major randomized phase III trials in 2011, sunitinib and everolimus have been considered as new therapeutic options for well-differentiated, advanced and progressive pancreatic NETs. For everolimus, another phase III study, although non-significant with the chosen criteria, showed effectiveness notably against small intestine NETs. These targeted therapies are new therapeutic weapons in management of well-differentiated DNETs, but its exact role in care strategy, in comparison with other treatments (somatostatin analogs, chemo-embolization, chemotherapy...) deserves to be precise in the future.

Colonic and rectal NET's

Neuroendocrine tumours of the Colon and Rectum are rare but are increasing in incidence as a result of greater investigation with endoscopy and improved histological reporting. Classification with the 2010 WHO TNM staging system as well as grading based on the Ki-67 index has led to improved prognostic assessment. The use of Endoanal Ultrasound has increased the sensitivity of detection of depth of invasion and lymphovascular involvement, which is associated with a poor prognosis. Standard polypectomy has largely been replaced by endoscopic mucosal resection of smaller polyps, although newer techniques such as band ligation or endoscopic submucosal dissection are likely to be associated with less residual disease. The management of advanced disease remains a challenge but new treatments such as Peptide Receptor Targeted therapy and molecular targeted treatments offer hope of improved progression free survival in non-resectable disease.

Sunitinib in advanced pancreatic neuroendocrine tumors: latest evidence and clinical potential

Based on preclinical data available in the RIP1-Tag2 transgenic mouse model, sunitinib is an inhibitor of angiogenesis in pancreatic neuroendocrine tumors blocking vascular endothelial growth factor receptors and platelet-derived growth factor receptors in endothelial cells and pericytes, respectively. Evidence of objective response in phase I trials justified the initiation of a large phase II/III program using sunitinib in patients with advanced/metastatic well-differentiated pancreatic neuroendocrine tumors. In the phase II study, sunitinib showed potent antitumor activity and a safe toxicity profile. In a recent double-blind placebo-controlled randomized phase III trial, sunitinib doubled the progression-free survival of patients, induced objective responses, and reduced the risk of death of patients with advanced/metastatic well-differentiated tumors. These data allowed the approval of sunitinib in several countries including Europe and the United States of America. These recent data provide hope for patients with well-differentiated pancreatic neuroendocrine tumors and will change standards of care in this disease.

Hitting the target: where do molecularly targeted therapies fit in the treatment scheduling of neuroendocrine tumours?

Neuroendocrine tumours (NETs) are a rare and heterogeneous group of tumours whose incidence is increasing and their prevalence is now greater than that of any other upper gastrointestinal tumour. Diagnosis can be challenging, and up to 25% of patients present with metastatic disease. Following the recent FDA approval of two new molecularly targeted therapies for the treatment of advanced pancreatic NETs (pNETs), the first in 25 years, we review all systemic therapies and suggest where these newer targeted therapies fit in the treatment schedule for these challenging tumours. Clinical trial data relating to the routine use of sunitinib and everolimus in low-intermediate-grade pNETs are summarised alongside newer molecularly targeted agents undergoing clinical assessment in NETs. We particularly focus on the challenge of optimal scheduling of molecularly targeted treatments around existing systemic and localised treatment such as chemotherapy or radiotargeted therapy. We also discuss application of current evidence to subgroups of patients who have not so far been directly addressed such as those with poorer performance status or patients receiving radical surgery who may benefit from adjuvant treatment.

Gastroenteropancreatic neuroendocrine tumors: incidence and treatment outcome in a single institution in Korea

AIM

We studied to identify the clinicopathological features, treatment outcome, and prognostic factors for patients with gastrointestinal and hepatopancreaticobiliary neuroendocrine tumor (NET).

METHOD

Between February 2001 and May 2006, a total of 470 patients were diagnosed with NET arising from the gastrointestinal tract, pancreas, and hepatobiliary system. The retrospective patient cohort was obtained and analyzed.

RESULTS

The male to female ratio was 1.5:1, and the median age was 55 years (range, 16-81). The most common primary site was the rectum (55.8%). Overall 29 (6.2%) originated from the hepatobiliary system. At initial presentation, 60 patients (12.8%) showed distant metastases. Curative surgery or endoscopic resection was performed in 401 patients. Histopathological distributions were as follows: well differentiated tumor (82.1%), well differentiated carcinoma (10.2%) and poorly differentiated carcinoma (7.7%). The frequency of the poorly differentiated type was somewhat higher in the hepatobiliary system than in the pancreas and gastrointestinal tract (44.8, 15.4 and 2.8%, respectively, P < 0.05). The estimated 5-year overall survival rate for all patients was 89.6%. Multivariate analysis showed that distant metastases (P = 0.018), origin from the hepatobiliary system (P < 0.001) and poorly differentiated neuroendocrine carcinoma (P < 0.001) were independent predictors for poor survival outcome.

CONCLUSION

Patients with locoregional NET had a favorable long-term survival after curative resection. Distant metastases, hepatobiliary localization and a poor degree of tumor cell differentiation were poor prognostic factors. Further investigational approaches for treatment of advanced disease are needed.

Neuroendocrine neoplasms of the gut and pancreas: new insights

Neuroendocrine neoplasms arise in almost every organ of the body and are variably defined according to the site of origin. This Review focuses on neuroendocrine neoplasms of the digestive tract and pancreas. The 2010 WHO classification of tumors of the digestive system introduces grading and staging tools for neuroendocrine neoplasms. A carcinoid is now defined as a grade 1 or 2 neuroendocrine tumor and grade 3, small-cell or large-cell carcinomas are defined as neuroendocrine carcinoma. Epidemiological data show a worldwide increase in the prevalence and incidence of gastroentero-pancreatic neuroendocrine tumors in the past few decades, which is probably due to improved methods of detection of these tumors. The current diagnostic procedures and treatment options for neuroendocrine neoplasms are defined and summarized in the Review, although evidence-based data are lacking. Surgery remains the treatment mainstay and somatostatin analogues the basis for both diagnosis and therapy as the only 'theranostic' tool. Emerging compounds including chemotherapeutic agents, small molecules and biological therapies may provide new hope for patients.

Therapy innovations: tyrosine kinase inhibitors for the treatment of pancreatic neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) show limited sensitivity to cytotoxic agents, requiring the search for novel therapies. Recently, data from a phase III trial demonstrated that sunitinib produces a clinically significant improvement in progression-free survival in patients with unresectable, advanced, or metastatic GEP-NETs. Based on this finding, sunitinib became the first targeted drug approved for the treatment of GEP-NETs, paving the way for the approval of other anticancer agents in this drug-orphan disease. To date, results of trials involving other multitargeted tyrosine kinase inhibitors, such as sorafenib, the monoclonal antibody bevacizumab, and insulin-like growth factor 1 receptor inhibitors, have also shown promising results, and some are already being studied in phase III trials. This review updates the results of ongoing trials using inhibitors of growth factors and tyrosine kinase receptors involved in the carcinogenesis of GEP-NETs.

Treatment of liver metastases in patients with neuroendocrine tumors: a comprehensive review

Patients diagnosed with Neuroendocrine Tumors (NET) often are also diagnosed with Neuroendocrine Liver Metastases (NLM) during the course of their disease. NLM can cause significant morbidity and mortality, oftentimes much more than compared to patients with NET. Treatment options have been limited in the past, focusing on surgical resections, for which only a minority of patients are candidates. However, developments of new treatment modalities have progressed rapidly and patients with NLM now have significantly more options, including surgical-directed therapies; liver-directed therapies; and nonsurgical, non-liver-directed therapies. This review provides information about the roles of hepatic resection, orthotopic liver resection, radiofrequency ablation, hepatic artery embolization and hepatic artery chemoembolization, hepatic artery radioembolization and selective internal radiation therapy, peptide receptor radionuclide therapy, systemic chemotherapy, biotherapies including somatostatin analogs and interferon-α, vascular endothelial growth factor and mTOR targets, and microRNA-regulated pathways. Given these new options, the clinician can tailor therapy specific to the patient diagnosed with NLM, thereby giving the patient the best possible chance of prolonged survival.

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.

Advances in the therapy of gastroenteropancreatic-neuroendocrine tumours (GEP-NETs)

Neuroendocrine tumours (NET) of the digestive tract comprise a broad range of malignancies. The therapeutic approach to these tumours has not evolved as it did in other tumour types in the last two decades. The deeper knowledge of the underlying molecular biology behind the growth of neuroendocrine cells has brought much information to light. We now know that somatostatin analogues may not only be considered as symptomatic treatment but also as antitumour agents. Sunitinib, a tyrosine kinase (TK) inhibitor with antiangiogenic and antitumoural properties, has been shown to induce significant improvement in progression-free survival in a randomised trial conducted in well-differentiated pancreatic islet-cell NETs. The relevance of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway seems to be crucial in gastroenteropancreatic (GEP)-NETs. In fact, mTOR inhibitors have shown activity in uncontrolled trials, and large, randomised trial results will be available shortly. In this article, we summarise the most recent available data on medical therapy for GEPNETs.

Liver-specific therapies for metastases of neuroendocrine pancreatic tumors

The presence or development of liver metastases in patients with neuroendocrine pancreatic tumors is the most important prognostic factor. Liver resection, transplantation and many different therapeutic approaches are discussed in this special review.