Systemic Treatment Selection for Patients with Advanced Pancreatic Neuroendocrine Tumours (PanNETs)

Pancreatic neuroendocrine tumours (PanNETs) are rare diseases and a good example of how research is not only feasible, but also of crucial importance in the scenario of rare tumours. Many clinical trials have been performed over the past two decades expanding therapeutic options for patients with advanced PanNETs. Adequate management relies on optimal selection of treatment, which may be challenging for clinicians due to the fact that multiple options of therapy are currently available. A number of therapies already exist, which are supported by data from phase III studies, including somatostatin analogues and targeted therapies (sunitinib and everolimus). In addition, chemotherapy remains an option, with temozolomide and capecitabine being one of the most popular doublets to use. Peptide receptor radionuclide therapy was successfully implemented in patients with well-differentiated gastro-entero-pancreatic neuroendocrine tumours, but with certain questions waiting to be solved for the management of PanNETs. Finally, the role of immunotherapy is still poorly understood. In this review, the data supporting current systemic treatment options for locally advanced or metastatic PanNETs are summarized. Strategies for treatment selection in patients with PanNETs based on patient, disease, or drug characteristics is provided, as well as a summary of current evidence on prognostic and predictive biomarkers. Future perspectives are discussed, focusing on current and forthcoming challenges and unmet needs of patients with these rare tumours.

An update on the management of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are a rare and heterogeneous group of neoplasia and differ in their clinical presentation, behavior, and prognosis based on both histological features and cancer stage at the time of diagnosis. Although small-sized tumors can be surgically resected, locally advanced and metastatic tumors confer a poor prognosis. In addition, only limited treatment options are available to the latter group of patients with PNETs, such as hormonal analogs, cytotoxic agents, and targeted therapy. In selected patients, liver-directed therapies are also used. As expected, clinicians taking care of these patients are challenged to develop an effective and comprehensive treatment strategy for their patients amid a wide variety of treatment modalities. Targeted therapy for PNETs is limited to sunitinib and everolimus. Presently, a number of clinical studies are ongoing to assess the efficacy of newer targeted agents alone and in combination with previous agents for the treatment of advanced PNETs. The authors reviewed the current treatment and also discussed the emerging agents and emphasized the need to identify biomarkers.

Small intestinal neuroendocrine tumours and fibrosis: an entangled conundrum

Small intestinal neuroendocrine tumours (SI-NETs) are neoplasms characterized by their ability to secrete biogenic amines and peptides. These cause distinct clinical pathology including carcinoid syndrome, marked by diarrhoea and flushing, as well as fibrosis, notably mesenteric fibrosis. Mesenteric fibrosis often results in significant morbidity by causing intestinal obstruction, oedema and ischaemia. Although advancements have been made to alleviate symptoms of carcinoid syndrome and prolong the survival of patients with SI-NETs, therapeutic options for patients with mesenteric fibrosis are still limited. As improved insight in the complex pathogenesis of mesenteric fibrosis is key to the development of new therapies, we evaluated the literature for known and putative mediators of fibrosis in SI-NETs. In this review, we discuss the tumour microenvironment, growth factors and signalling pathways involved in the complex process of fibrosis development and tumour progression in SI-NETs, in order to elucidate potential new avenues for scientific research and therapies to improve the management of patients suffering from the complications of mesenteric fibrosis.

Pancreatic neuroendocrine tumors: targeting the molecular basis of disease

PURPOSE OF REVIEW

Pancreatic neuroendocrine tumors (pNETs) are a rare and heterogeneous group of neoplasia. Presentation of these tumors can vary widely. Current treatment modalities range from potentially curative surgical interventions in localized disease to the use of varied hormonal analogues, cytotoxic agents and targeted therapy for the management of locally advanced and metastatic disease. With such a wide variety of therapeutic modalities, clinicians are faced with the task of building an effective and comprehensive treatment strategy for their patients.

RECENT FINDINGS

Targeted therapy for pNET is limited to sunitinib and everolimus. There have been a number of important studies assessing the efficacy of other targeted agents, in addition to the conjugation of these agents in the management of advanced pNET. This review will stand to highlight currently available targeted therapies for the treatment of advanced pNET.

SUMMARY

The use of targeted agents in the management of advanced pNET has significant potential to change the current standard of care. In addition to the use of long-acting somatostatin analogues, targeting the mammalian target of rapamycin and vascular endothelial growth factor pathways can be well tolerated and may lead to long periods of disease control in a wide variety of neuroendocrine tumors involving the pancreas.

Management of pancreatic neuroendocrine tumors

Abstract: 

Despite the rarity of the disease, there has been significant recent progress in the management of pancreatic neuroendocrine tumors (PNETs). Arterial phase imaging and somatostatin scintigraphy are important parts of the diagnostic and staging work-up of PNETs. The slow growth rate of PNETs can make observation a reasonable initial option in low volume asymptomatic disease or allow debulking surgery in selected patients with advanced disease. Somatostatin analogs, angiogenesis and mTOR inhibitors have proven benefit for PNET patients in randomized trials while retrospective and single-arm trials using chemotherapy or peptide receptor radiation therapy also appear promising. This review summarizes key aspects in the management of PNETs with emphasis on the most recent advances in systemic therapy.

Perfusion computed tomography as functional biomarker in randomized run-in study of bevacizumab and everolimus in well-differentiated neuroendocrine tumors

OBJECTIVES

This study aimed to assess the antitumor activity of everolimus and bevacizumab among patients with advanced neuroendocrine tumors and to assess perfusion computed tomography (CT) as a potential functional biomarker.

METHODS

Patients with low- to intermediate-grade neuroendocrine tumors received one 3-week cycle of 15 mg/kg of bevacizumab on day 1 or 10 mg of everolimus daily. Subsequent cycles consisted of the combination of both drugs. Perfusion CTs were performed at baseline and at the end of cycles 1 and 3.

RESULTS

Therapy decreased blood flow (BF) proportional to baseline measurements. Bevacizumab was associated with a 44% decrease in BF (P < 0.0001). After the addition of everolimus, a further 29% decrease (P = 0.02) in BF was observed. Everolimus alone was associated with 13% increase in mean transit time (P = 0.02). Clinical activity was demonstrated, with a confirmed response rate of 21% and a median progression-free survival of 14.6 (95% confidence interval, 13.0-16.1) months. Pretreatment tumor permeability surface (P = 0.009), posttreatment mean transit time (P = 0.003), percent reduction in BF (P = 0.03), and percent reduction in blood volume (P = 0.002) were associated with best percent reduction in tumor diameters.

CONCLUSIONS

Bevacizumab and everolimus demonstrated antitumor activity. Perfusion CT is a promising tool for the development of antiangiogenic strategies and for the selection of patients who are likely to benefit from therapy.

Current clinical trials of targeted agents for well-differentiated neuroendocrine tumors

Neuroendocrine tumors (NETs) are a group of tumors originating in various locations, including the gastrointestinal tract, lung, and pancreas. Clinical trial design and disease management of these tumors pose a significant challenge because of the heterogeneous clinical presentations and varying degrees of aggressiveness. The recent completion of several phase II and III trials demonstrates that rigorous investigation of novel agents can lead to practice-changing outcomes. Furthermore, the molecular and genetic understanding of NETs has dramatically improved during the last few years; as a result, investigators have shifted clinical trial design to focus on targeted therapies. Most of these trials have targeted the somatostatin, vascular endothelial growth factor, and mammalian target of rapamycin pathways. This review will discuss the NET treatment landscape and trials of targeted agents currently offered.

Bevacizumab combined with 5-FU/streptozocin in patients with progressive metastatic well-differentiated pancreatic endocrine tumours (BETTER trial)--a phase II non-randomised trial

AIM OF THE STUDY

Neuroendocrine tumours are highly vascular neoplasms known to overexpress vascular endothelial growth factor (VEGF) and its receptor. Bevacizumab, an inhibitor of VEGF, was assessed in combination with chemotherapy in pancreatic neuroendocrine tumour (P-NET).

PATIENTS AND METHODS

BETTER was a multicentre, open-label, non-randomised, two-group phase II trial. Patients with progressive metastatic, well-differentiated P-NET received a minimum of 6 month treatment of bevacizumab at 7.5 mg/kg IV on d1 q3w with 5-FU at 400 mg/m2/day and streptozocin at 500 mg/m2/day IV from d1 to d5 every 42 days. The primary end-point was progression-free survival (PFS); secondary end-points were overall survival (OS), overall response rate, safety and quality of life.

RESULTS

A total of 34 patients were included. Median age was 55 years, 65% of patients were men, 97% had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 and 97% had a Ki-67 proliferative index of <15%. After a maximum of 24 month follow-up per patient, the median PFS assessed by investigators was 23.7 months [95% confidence interval (CI): 13.1; not reached], 19 (56%) patients had a partial response and 15 (44%) had stable disease as best response. OS rate at 24 months was 88%. The most frequently reported grade 3-4 adverse events were hypertension (21% patients), abdominal pain (12%) and thromboembolic events (9%).

CONCLUSION

Bevacizumab with 5-FU/streptozocin in the treatment of pancreatic NETs seems to be feasible with a PFS of 23.7 months, which deserves further attention. No unexpected toxicity was observed.

Bevacizumab plus capecitabine in patients with progressive advanced well-differentiated neuroendocrine tumors of the gastro-intestinal (GI-NETs) tract (BETTER trial)--a phase II non-randomised trial

AIM OF THE STUDY

Gastro-intestinal neuroendocrine tumours (GI-NETs) are chemotherapy-resistant tumours. Bevacizumab, an inhibitor of vascular endothelial growth factor (VEGF), has shown promising results in several phase II trials of gastro-entero-pancreatic-NETs. We assessed bevacizumab combined with capecitabine, specifically in GI-NET patients.

PATIENTS AND METHODS

BEvacizumab in The Treament of neuroEndocrine tumoRs (BETTER) was a multicentre, open-label, non-randomised, two-group phase II trial. Here we present the group of patients with progressive, metastatic, well-differentiated GI-NETs. Patients Eastern Cooperative Oncology Group-performance status (ECOG-PS)⩽2, Ki-67 proliferation rate <15% and no prior systemic chemotherapy were treated with bevacizumab (7.5 mg/kg/q3w) and capecitabine (1000 mg/m2 twice daily, orally d1-14, resumed on d22) for 6-24 months. The primary end-point was progression-free survival (PFS); secondary end-points included overall survival (OS), response rate, safety and quality of life.

RESULTS

Of the 49 patients included, 53% were men, median age was 60 years (41-82), primary tumour site was ileal in 82% patients and Ki-67 was <15% in 48 patients and not available for one patient. After a maximum of 24 month follow-up per patient, the median PFS by investigator assessment was 23.4 months [95% confidence interval (CI): 13.2; not reached] and the overall disease control rate was 88% (18% partial response, 70% stable disease). The 2-year survival rate was 85%. Median OS was not reached. The most frequent grade 3-4 adverse events were hypertension (31%), diarrhoea (14%) and hand-foot syndrome (10%).

CONCLUSION

The combination of bevacizumab and capecitabine showed clinical activity and a manageable safety profile in the treatment of GI-NETs that warrant confirmation in a randomised phase III trial.

A tale of two tumors: treating pancreatic and extrapancreatic neuroendocrine tumors

Despite their perceived rarity, gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rising in incidence and prevalence. The biology, natural history, and therapeutic options for GEP-NETs are heterogeneous: NETs arising in the pancreas can be distinguished from those arising elsewhere in the gastrointestinal tract, and therapy is dichotomized between these two groups. Somatostatin analogues are the mainstay of oncologic management of bowel NETs; everolimus, streptozocin, and sunitinib are approved to treat pancreatic NETs. There are significant differences in molecular genetics between pancreatic and extrapancreatic NETs, and studies are evaluating whether additional NET patients may benefit from targeted agents. We discuss the distinguishing features of these two groups of tumors, as well as the therapeutic implications of the distinction. We also examine the evolving therapeutic landscape and discuss the likelihood that treatment will be developed independently for pancreatic and extrapancreatic gastrointestinal NETs, with novel therapeutics effective for newly identified pathologically or molecularly defined subgroups.

Targeting the mTOR signaling pathway in neuroendocrine tumors

OPINION STATEMENT

Neuroendocrine tumors (NETs) are a heterogeneous group of malignancies characterized by variable but most often indolent biologic behavior. Well-differentiated NETs can be broadly classified as either carcinoid or pancreatic NET. Although they have similar characteristics on routine histologic evaluation, the 2 tumor subtypes have different biology and respond differently to treatment, with most therapeutic agents demonstrating higher response rates in pancreatic NETs compared with carcinoid. Until recently, systemic treatment options for patients with advanced NETs were limited. However, improvements in our understanding of signaling pathways involved in the pathogenesis, growth, and spread of NETs have translated into an expansion of treatment options. Aberrant signaling through the mechanistic pathway of rapamycin (mTOR) pathway has been implicated in neuroendocrine tumorigenesis. Additionally, altered expression of mTOR pathway components has been observed in NETs and has been associated with clinical outcomes. Targeting the mTOR pathway has emerged as an effective treatment strategy in the management of advanced NETs. In a randomized, placebo-controlled study of patients with advanced pancreatic NET, treatment with the mTOR inhibitor everolimus was associated with improved progression-free survival (PFS). Largely based upon these data, everolimus has been approved in the United States and Europe for the treatment of patients with advanced pancreatic NET. The activity of everolimus remains under investigation in patients with carcinoid tumors. In a randomized study of patients with advanced carcinoid tumors associated with carcinoid syndrome, the addition of everolimus to octreotide was associated with improved PFS compared with octreotide. However, the results did not meet the prespecified level of statistical significance based on central review of radiographic imaging. Results from a randomized study examining the efficacy of everolimus in patients with nonfunctional gastrointestinal and lung NETs are awaited. In addition, further investigation is needed to determine whether primary tumor site or other clinical and molecular factors can impact response to mTOR inhibition. Although everolimus can slow tumor progression, significant tumor reduction is rarely obtained. Targeting multiple signaling pathways is a treatment strategy that may provide better tumor control and overcome resistance mechanisms involved with targeting a single pathway. Results of ongoing and future studies will provide important information regarding the added benefit of combining mTOR inhibitors with other targeted agents, such as VEGF pathway inhibitors, and cytotoxic chemotherapy in the treatment of advanced NETs.

[Malignant insulinoma: recommendations for workup and treatment]

Insulinoma are malignant in 4 to 14 % of cases. Their rarity and the sparse data available in the literature have limited publication of specific guidelines for their management. The following review aim to provide up-to-date recommendations on initial evaluation including pathologic grading, measures to control hypoglycemia, antitumor strategies and long term follow-up. Will be discussed in detail respective indications of surgery, diazoxide, somatostatin analogs, everolimus, sunitinib, liver directed treatments including arterial embolization, chemotherapy and radiometabolic therapy. A Medline search using terms "insulinoma", "neuroendocrine pancreatic tumors", "islet cell carcinoma", "malignant insulinoma" was performed limiting the selection to English language articles and adult age cases, along with cross referencing.

Phase II study of pazopanib monotherapy in metastatic gastroenteropancreatic neuroendocrine tumours

BACKGROUND

Treatment options for patients with metastatic gastroenteropancreatic neuroendocrine tumours (GEP NETs) are still limited. We investigated the antitumour activity and safety profile of pazopanib--a multitarget drug with anti-angiogenic activity in patients with metastatic GEP NETs.

METHODS

This was a nonrandomised, open-labeled, single-center phase II study. Pazopanib was orally administered at a dose of 800 mg daily continuously with a 28-day cycle. The primary end point was an objective response rate according to Response Evaluation Criteria in Solid Tumors (RECIST). The secondary end points were progression-free survival (PFS), overall survival (OS) and safety. An independent review of objective response was planned. The trial is registered with ClinicalTrials.gov, NCT number 01099540. Correlative biomarker analyses were performed.

RESULTS

Between April 2010 and February 2012, a total of 37 patients were enrolled. Thirty-two percent of the enrolled patients had pancreatic primary and 22% of the patients had colorectal primary NETs. This phase II study demonstrated an objective response rate of 18.9% (7 of the 37, 95% CI 8.0-35.2) and a disease control rate (CR+confirmed PR+stable disease) of 75.7% (28 of the 37, 95% CI, 58.8-88.2) in metastatic GEP NETs. The independent review demonstrated a higher overall response rate of 24.3% (95% CI, 11.8-41.2%) with nine confirmed PRs.

CONCLUSION

Pazopanib showed a comparable efficacy to other targeted agents not only in pancreatic NETs but also in NETs originating from gastrointestinal (GI) tract.

Management of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors account for 1% to 2% of pancreatic neoplasms and may occur sporadically or as part of a hereditary syndrome. Patients may present with symptoms related to hormone secretion by functional tumors or to locally advanced or metastatic nonfunctional tumors. Asymptomatic pancreatic neuroendocrine tumors are increasingly detected incidentally during abdominal imaging performed for other reasons. The management of localized pancreatic neuroendocrine tumors is surgical resection. Hepatic metastases are common and their management involves a variety of liver-directed therapies, which should be tailored according to extent of disease, symptoms, presence of extrahepatic metastases, and patient performance status.

Safety and efficacy of sunitinib in patients with unresectable pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are becoming increasingly common, with the majority of patients presenting with either lymph node involvement or metastatic disease, thus requiring systemic therapy. Targeted therapy is a type of medication that blocks the growth of cancer cells by interfering with specific targeted molecules needed for carcinogenesis and tumor growth rather than by simply interfering with rapidly dividing cells (eg, with traditional chemotherapy). In this review article, pharmacologic inhibition of multiple targets including vascular endothelial growth factor receptor (VEGF-R), platelet-derived growth factor receptor (PDGF-R), stem cell factor receptor (c-KIT-R), FML-like tyrosine kinase-3 receptor (FLT3-R), colony stimulating factor 1 receptor (CSF1-R), and glial cell-line derived neurotrophic factor receptor (RET-R) with sunitinib in patients with unresectable PNETs is discussed. Phase III data indicate that additional treatment with sunitinib can improve prognosis in these patients.

A shining light in the darkness for the treatment of pancreatic neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors are rare neoplasms; past decades have seen limited research channeled into this area. Recently, 2 placebo-controlled phase III trials using 2 drugs--everolimus and sunitinib--with distinct molecular rationales achieved their principal objective of increasing survival in patients with advanced pancreatic neuroendocrine tumors (PNET). Nonetheless, several questions remain unanswered, notably defining the optimal schedule for integrating these targeted agents with conventional cytotoxics and other treatment options, and identifying appropriate biomarkers for patients with the potential to derive greater benefit. In this article, we analyze the results of the 2 largest studies ever completed in patients with PNETs and discuss the challenges for future drug development in this setting.

SUMMARY

Sunitinib and everolimus will become new treatment options for patients with PNETs and will be integrated into the complex therapeutic management of this disease. In this review, we summarize the evidence-based data of these drugs as well as the molecular-based science in this setting that will lay the groundwork for future studies.

Pancreatic neuroendocrine tumors: a comprehensive review

Pancreatic neuroendocrine tumors (NETs) are a heterogeneous group of tumors. Despite being relatively rare, representing just 1-2% of all pancreatic neoplasms, the incidence of pancreatic NET has increased over the past two decades. Although the primary treatment for localized NET is surgical resection, there is still a lack of effective therapeutic options for patients with advanced unresectable pancreatic NET. Recently, the targeted agents sunitinib malate (SUTENT®, Pfizer Inc, NYC) and everolimus (AFINITOR®, Novartis, Basel, Switzerland)-both with different mechanisms of action-received United States Food and Drug Administration approval for the treatment of progressive, well-differentiated, pancreatic NET in patients with unresectable, locally advanced or metastatic disease. SUTENT® also received approval for this indication by the European Commission in 2010. Our article presents an overview of pancreatic NET, with a focus on their diagnostic work-up, clinical presentation and treatment options. Topics for further investigation of targeted therapy are also discussed.

A new era for the systemic therapy of neuroendocrine tumors

Carcinoids and pancreatic neuroendocrine tumors are becoming increasingly common, with the majority of patients presenting with either lymph node involvement or metastatic disease. An improved understanding of the molecular mechanisms involved in these tumors has implicated several pathways that have led to new therapeutic approaches. In this manuscript, we describe the biology of neuroendocrine tumors and approaches to systemic therapy. We review early data regarding the use of cytotoxics and several recent studies employing more targeted approaches that promise to change the standard of care. Specifically, phase III studies indicate that pharmacologic inhibition of the vascular endothelial growth factor pathway with sunitinib, and of the mammalian target of rapamycin pathway with everolimus, appears to have altered the natural history of these diseases. These successes set the stage for further advances in the management of patients with neuroendocrine tumors.

New strategies for advanced neuroendocrine tumors in the era of targeted therapy

Low- to intermediate-grade neuroendocrine tumor (NET) constitutes a group of indolent malignancies that share the capacity for secreting hormones and neuroamines. Until recently, there were few therapeutic options for oncologic control. The PROMID study showed that octreotide long-acting repeatable formulation can delay tumor growth in midgut NETs. And, recent phase III studies showed both everolimus and sunitinib improved progression-free survival in pancreatic NETs, validating the phosphoinositide 3-kinase/Akt/mTOR pathway and angiogenesis as important targets for further advances. Ongoing and planned pivotal studies targeting these pathways in other NET subtypes may widen their therapeutic application. Development of rational combinations may further improve therapeutic outcome. These successes and our improved understanding of the underlying molecular biology are likely to lead to further important advances on the horizon.

Medical treatment of gastroenteropancreatic neuroendocrine tumors

Treatment of the clinically and prognostically heterogeneous neuroendocrine neoplasms (NEN) should be based on a multidisciplinary approach, including surgical, interventional, medical and nuclear medicine-based therapeutic options. Medical therapies include somatostatin analogues, interferon-α, mTOR inhibitors, multikinase inhibitors and systemic chemotherapy. For the selection of the appropriate medical treatment the hormonal activity, primary tumor localization, tumor grading and growth behaviour as well as the extent of the disease must be considered. Somatostatin analogues are mainly indicated in hormonally active tumors for symptomatic relief, but antiproliferative effects have also been demonstrated, especially in well-differentiated intestinal NET. The efficacy of everolimus and sunitinib in patients with pancreatic neuroendocrine tumors (pNET) has been demonstrated in large placebo-controlled clinical trials. pNETs are also chemosensitive. Streptozocin-based chemotherapeutic regimens are regarded as current standard of care. Temozolomide in combination with capecitabine is an alternative that has shown promising results that need to be confirmed in larger trials. Currently, no comparative studies and no molecular markers are established that predict the response to medical treatment. Therefore the choice of treatment for each pNET patient is based on individual parameters taking into account the patient’s preference, expected side effects and established response criteria such as proliferation rate and tumor load. Platin-based chemotherapy is still the standard treatment for poorly differentiated neuroendocrine carcinomas. Clearly, there is an unmet need for new systemic treatment options in patients with extrapancreatic neuroendocrine tumors.

New treatment options for patients with advanced neuroendocrine tumors

Well- to moderately differentiated neuroendocrine tumors (NET) are a heterogeneous group of malignancies for which a range of therapeutic options have been employed. For patients with localized NET, surgical resection remains the mainstay of treatment. Surgical resection of hepatic metastases or hepatic artery embolization may also be beneficial in patients with hepatic-predominant metastatic disease. Symptoms of hormonal excess, such as carcinoid syndrome and syndromes associated with functional pancreatic NET, can be effectively treated with somatostatin analogs. Systemic treatment options for patients with advanced NET have been limited. Treatment with the somatostatin analog octreotide has been shown to improve progression-free survival in patients with advanced midgut carcinoid tumors, and the potential antiproliferative effect of somatostatin analogs in patients with other NET subtypes is currently under investigation. Patients with advanced pancreatic NET may also respond to treatment with streptozocin or temozolomide-based therapy. In patients with advanced pancreatic NET, randomized, placebo-controlled studies have recently demonstrated that treatment with the tyrosine kinase inhibitor sunitinib or with the mTOR inhibitor everolimus is associated with improved progression-free survival. Based on these studies, sunitinib or everolimus should now be considered as therapeutic options in patients with advanced pancreatic NET. Initial phase II studies have also suggested activity associated with VEGF pathway and mTOR inhibitors in patients with advanced carcinoid tumors. Future studies will likely further define the role of these agents in the advanced carcinoid patient population.

Overcoming antiangiogenic resistance

The success of drugs targeting angiogenesis is tempered by the transient duration of disease control and modest survival improvement. The very hypoxic stress produced by successful therapy may lead to upregulation of multiple pathways that promote angiogenesis and invasive behavior. Overcoming this evasive resistance may further improve outcome.

Future directions in the treatment of neuroendocrine tumors: consensus report of the National Cancer Institute Neuroendocrine Tumor clinical trials planning meeting

Neuroendocrine tumors (NETs) arise from a variety of anatomic sites and share the capacity for production of hormones and vasoactive peptides. Because of their perceived rarity, NETs have not historically been a focus of rigorous clinical research. However, the diagnosed incidence of NETs has been increasing, and the estimated prevalence in the United States exceeds 100,000 individuals. The recent completion of several phase III studies, including those evaluating octreotide, sunitinib, and everolimus, has demonstrated that rigorous evaluation of novel agents in this disease is both feasible and can lead to practice-changing outcomes. The NET Task Force of the National Cancer Institute GI Steering Committee convened a clinical trials planning meeting to identify key unmet needs, develop appropriate study end points, standardize clinical trial inclusion criteria, and formulate priorities for future NET studies for the US cooperative group program. Emphasis was placed on the development of well-designed clinical trials with clearly defined efficacy criteria. Key recommendations include the evaluation of pancreatic NET separately from NETs of other sites and the exclusion of patients with poorly differentiated histologies from trials focused on low-grade histologies. Studies evaluating novel agents for the control of hormonal syndromes should avoid somatostatin analog washout periods when possible and should include quality-of-life end points. Because of the observed long survival after progression of many patients, progression-free survival is recommended as a feasible and relevant primary end point for both phase III studies and phase II studies where a delay in progression is expected in the absence of radiologic responses.

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.