Phase II study of thalidomide in patients with metastatic carcinoid and islet cell tumors

Systemic Therapies for Metastatic Pancreatic Neuroendocrine Tumors

OPINION STATEMENT

Over the years, there have been significant advances in systemic treatments for metastatic pancreatic neuroendocrine tumors (panNETs). Despite these advancements, uncertainty remains regarding how to best sequence available therapies. For well-differentiated and metastatic panNETs that are somatostatin receptor (SSTR) avid on functional imaging, first-line therapy typically consists of somatostatin analogs (SSAs), given their favorable toxicity profile and overall low burden for patients. When progression of disease is observed on an SSA, multiple treatment options are available, including the targeted agents everolimus and sunitinib, peptide receptor radionuclide therapy (PRRT), as well as chemotherapy, with the latter often preferred for those panNETs of heavy tumor burden, higher grade, and/or more aggressive behavior clinically and/or radiographically. Here, we review panNET classification, currently available systemic treatments, therapy sequencing, and areas of active investigation to further our treatments for the disease.

Chemotherapy in NETs: When and how

The majority of neuroendocrine tumours (NETs) are well-differentiated tumours that follow an indolent course, in contrast to a minority of poorly differentiated neuroendocrine carcinomas (NECs) which exhibit an aggressive course and assocaited with an overall short survival. Although surgery is the only curative treatment for NETs it is not always feasible,necessitating the application of other therapies including chemotherapy. Streptozotocin (STZ)-based regimens have long been used for advanced or metastatic well-to-moderately differentiated (G1-G2) NETs, especially those originating from the pancreas (pNETs). In poorly differentiated grade 3 (G3) tumours, platinum-based chemotherapy is recommended as first-line therapy, albeit without durable responses. Although data for temozolomide (TMZ)-based chemotherapy are still evolving, this treatment may replace STZ-based regimens in pNETs due to its better tolerability and side effect profile. In addition, there is evidence that TMZ could also be used in the subgroup of well-differentiated G3 NETs. There is less clear-cut evidence of a benefit for chemotherapy in intestinal NETs, but still evolving data suggest that TMZ may be efficacious in particular patients. In lung and thymic carcinoids, chemotherapy is reserved for patients with progressive metastatic disease in whom other treatment options are unavailable. Overall, chemotherapy is indicated in patients who have progressed on first-line treatment with somatostatin analogues, have extensive tumour load or exhibit rapid growth following a period of follow-up, and/or have a high proliferative rate; it may occasionally can be used in a neo-adjuvant setting. Prospective randomised studies are awaited to substantiate the role of chemotherapy in the therapeutic algorithm of NETs along with other evolving treatments.

Chemotherapy for advanced non-pancreatic well-differentiated neuroendocrine tumours of the gastrointestinal tract, a systematic review and meta-analysis: A lost cause?

BACKGROUND

Chemotherapy is well-established in the treatment of patients with well-differentiated neuroendocrine tumours (NETs) arising from the pancreas (pNETs); however, its role in patients with gastrointestinal non-pancreatic NETs (non-pNETs) is uncertain. This systematic review assesses the evidence for the role of chemotherapy in well-differentiated non-pNET patients.

METHODS

Eligible studies (identified using MEDLINE) were those reporting response and/or survival data for patients with well-differentiated non-pNETs receiving systemic chemotherapy. The primary end-point was overall-response (OR) rate; secondary end-points were progression-free survival (PFS), overall survival (OS), disease-stabilization (DS) and disease-control (DC) rates.

RESULTS

Of 6434 studies screened, 20 were eligible: one randomised phase III trial, 2 randomised phase II studies, 10 single-arm phase II trials and 7 retrospective analyses including a total of 264 patients (median of 11 patients per study, range 6-49); and employing multiple chemotherapy schedules. The mean "median PFS" and "median OS" were 16.9 months (95%-confidence interval (CI) 3.8-30.04) and 32.2 months (95%-CI 10.4-54.2), respectively. The non-weighted mean OR, DS and DC rates were 11.5% (95%-CI 5.8-17.2), 56.5% (95%-CI 38.1-74.9) and 70.7% (95%-CI 54.9-86.5), respectively. In studies including both pNETs and non-pNET patients, meta-analysis showed a lower OR-rate in the non-pNET patients when compared to pNETs [odds ratio (OR) 0.35 (95% CI 0.18-0.66)]; however significance was lost when high-risk bias studies were excluded in a sensitivity analysis [OR 0.45 (95% CI 0.19-1.07); p-value 0.07].

CONCLUSION

Studies were of evidence level-C with heterogeneous populations and treatments; and small patient numbers. Well-designed, prospective studies are needed to adequately evaluate the role of chemotherapy in this setting.

Systemic Therapies for Advanced Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors are an uncommon tumor type and compose 1% to 2% of all pancreatic neoplasms. They are rarely localized at presentation and are typically diagnosed in the presence of metastatic disease. The management poses a significant challenge because of the heterogeneous clinical presentations and varying degrees of aggressiveness. A variety of systemic therapies have been developed for the management of pancreatic neuroendocrine tumors, including somatostatin analogues, a select group of cytotoxic chemotherapy agents, and targeted or biological agents. This article reviews the available systemic therapy options for advanced pancreatic neuroendocrine tumors.

Unusual endoscopic findings of gastric neuroendocrine tumor

Gastric neuroendocrine tumor (NET) is sometimes found as a submucosal tumor on upper gastrointestinal endoscopy. Gastric NET with malignant profile and neuroendocrine carcinoma (NEC) show various forms which are difficult to distinguish from gastric cancer and other disease. We report a case of a cauliflower-shaped NET of the stomach. A 61-year-old man was referred to our hospital with a complaint of abdominal fullness. Upper gastrointestinal endoscopic examination revealed an unusual, whitish cauliflower-shaped tumor that belongs to Borrmann type I on the lesser curvature of the gastric antrum. Histological examination of the biopsy specimen revealed NET G2, because the tumor cells were CD56- and synaptophysin-positive by immunohistochemical analysis. A distal gastrectomy with D2 lymphadenectomy was performed. A recurrence in the liver was revealed by follow up computed tomography after 11 months from operation. Combined chemotherapy with irinotecan (CPT-11) plus cisplatin (CDDP) was treated. The patient achieved a partial response, but he died after 31 months from gastrectomy. There is no independent, large-scaled prospective study and no standard treatment for gastric NETs with distant metastases. Our case is reported with a literature review of the treatment of metastatic gastric NET G2.

Bone metastases in well-to-moderately differentiated neuroendocrine tumors: a single institutional review from the Ohio State University Medical Center

OBJECTIVE

In this study, we look at the clinical features associated with bone metastasis in patients with well-to-moderately differentiated neuroendocrine tumors (NETs), specifically primary tumor characteristics, complications, elevated hormone levels, and survival.

METHODS

A retrospective study at the Ohio State University was performed on patients diagnosed with well-to-moderately differentiated NETs from 2000 to 2010 who were found to have bone metastases. A control group of patients with metastatic NETs without bone metastases was matched with regard to demographic and clinical data.

RESULTS

Of 341 patients with well-to-moderately differentiated NETs, 40 patients were found with bone metastases within the 10-year study period. Patients with bone metastases had shorter survival (median, 52 months) compared to the control group (median, 98 months; P = 0.024). Of 26 patients with bone metastases who died, 6 (23%) patients had a cause of death related to their bone metastatic disease. There were 8 patients with spinal cord compression, and 6 with pathologic fractures.

CONCLUSIONS

Our study suggests that patients with well-to-moderately differentiated NETs metastatic to bone have larger tumors, more frequently elevated pancreastatin, and shorter survival than patients without bone metastases, with complications of bone metastases significantly contributing to mortality and morbidity.

Vascular endothelial growth factor (VEGF) pathway and neuroendocrine neoplasms (NENs): prognostic and therapeutic considerations

Neuroendocrine neoplasms (NENs) consist of a large heterogeneous group of epithelial tumors with neuroendocrine differentiation, as proved by immune reactivity for neuroendocrine markers. From the very first studies of vascular endothelial growth factor (VEGF) pathway, VEGF has been considered an important prognostic marker in NENs. Consequently, a number of preclinical experiences and clinical trials have examined the efficacy of VEGF-targeted therapeutics in NENs. Bevacizumab and sorafenib were clinically tested in NENs and they showed modest activity, while on the other hand, they present significant toxicity problems. More interesting in gastroenteropancreatic (GEP)-NENs seems to be the demonstrated efficacy of sunitinib. Preclinical as well as clinical sunitinib data in this regard provide a new hope in that direction. The use of other novel VEGF-targeted agents like aflibercept as well as VEGFR-TKI is being investigated in a number of phase II studies; the results of which are greatly awaited. Additionally, the use of potential biomarkers to select patients for VEGF-targeted therapy may be considered for further clinical evaluation. Thus, this article reviews the basic science as well as clinical data of VEGF signaling in advanced NENs with special emphasis on the different VEGF-targeting agents tested previously in this disease and the future prospective in that field.

Bevacizumab-based combination therapy for advanced gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs): a systematic review of the literature

BACKGROUND

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) consist of a large heterogeneous group of epithelial tumors with neuroendocrine differentiation that arises in gastrointestinal tract and pancreatic tissues. Advanced GEP-NENs are considered distinct disease entity with limited approved treatment options and poor prognosis. So, we will explore in this systematic review the value of using bevacizumab-based combination in this subset of NENs.

METHODS

PubMed, Medline, the Cochrane Library, trip database and Google Scholar were searched using the terms "GEP-NENs" OR "Gastroenteropancreatic neuroendocrine tumors" AND "systemic anticancer therapy" AND "Bevacizumab" and selecting only the English literature. Outcomes of interest included progression-free survival and overall survival (PFS and OS), tumor response and toxicities.

RESULTS

A total of 17 potentially relevant trials were identified, of which eight studies were excluded. Hence, nine trials involving 320 patients were included. Median PFS was reported in eight out of the nine studies ranging from 8.2 to 16.5 months. Median OS was reported in one study, and it was 33.3 months for the whole group. The disease control rate was reported in the seven studies, and it ranged from 80 to 96%. The overall response rate was reported in eight studies, and it ranged from 0 to 64%. Frequently reported grade 3/4 toxicities were gastrointestinal toxicities, mucocutaneous toxicities and hematologic toxicities (particularly leucopenia).

CONCLUSIONS

The current evidence from the available clinical trials suggests that bevacizumab in combination with some other anticancer agents (especially mTOR inhibitors and interferons) could be a more effective and tolerable treatment for advanced GEP-NENs in the future. However, such bevacizumab-based combination cannot be recommended outside the setting of clinical trials.

Hallmarks of gastrointestinal neuroendocrine tumours: implications for treatment

In the past few years, there have been advances in the treatment of neuroendocrine tumours (NETs) and improvements in our understanding of NET biology. However, the benefits to patients have been relatively modest and much remains yet to be done. The 'Hallmarks of Cancer', as defined by Hanahan and Weinberg, provide a conceptual framework for understanding the aberrations that underlie tumourigenesis and to help identify potential targets for therapy. In this study, our objective is to review the major molecular characteristics of NETs, based on the recently modified 'Hallmarks of Cancer', and highlight areas that require further research.

Pancreatic neuroendocrine tumors: approach to treatment with focus on sunitinib

Pancreatic neuroendocrine tumors (pNETs) are relatively rare malignancies. With secretory tumors such as insulinomas, vasoactive intestinal peptideomas, and gastrinomas, the hormone produced causes the symptom complex (e.g. hypoglycemia, peptic ulcer disease). With nonsecretory NETs, the clinical condition is determined by tumoral growth and metastasis. The course of metastatic pNETs may be indolent for several years but progression is often more rapid at later stages, leading to significant disability and a markedly negative impact on quality of life. Until recently, there were few effective systemic treatments for pNETs. Standard chemotherapy produces limited responses and has considerable toxicity. Somatostatin analogues control symptoms in some types of pNETs, but have not yet demonstrated antitumor activity. The recent introduction of targeted therapies, including the tyrosine kinase inhibitor sunitinib and the mammalian target of rapamycin inhibitor everolimus, yielded new opportunities for patients with advanced/metastatic pNETs. These drugs, which target key pathways in tumor proliferation and angiogenesis, provided clear clinical benefits in phase III clinical trials, including delayed tumor progression. The pivotal sunitinib phase III trial was discontinued prematurely due to higher rates of death and serious adverse events with placebo and greater progression-free survival (PFS) with sunitinib. In this trial, sunitinib demonstrated encouraging long-term responses as well as PFS and overall survival benefits, and an acceptable safety profile that allowed patients to preserve their quality of life. In every patient subgroup, including secretory and nonsecretory tumors, the hazard ratio for progression or death favored sunitinib. Circulating biomarkers are being investigated for the prediction and monitoring of responses to sunitinib. Although not fully evaluated in pNETs, biomarkers associated with response to sunitinib in several tumor types include soluble vascular endothelial growth factor receptor 2 and 3, interleukin 8, and stromal cell-derived factor 1α. Based on recent data, treatment algorithms have been updated for advanced and metastatic pNETs.

Systemic therapeutic options for carcinoid

"Carcinoids" are mostly slow-growing neuroendocrine neoplasms (NENs) with low proliferative activity. A wide range of therapeutic options with variable efficacy exist, including locoregional ablative strategies. Thereafter, some patients may not require medical therapy for years depending on the rate of progression or recurrence. However, the majority of patients require systemic treatment and therein lies the dilemma, since no antiproliferative agent is currently approved for carcinoids. Somatostatin analogs (SSAs), and to a lesser extent interferon-alpha, are standard therapy for carcinoids associated with the carcinoid syndrome. These drugs have some antiproliferative efficacy. SSAs rarely lead to tumor remission but may modestly prolong time to tumor progression. Chemotherapy is of limited value in carcinoids with low proliferation indices but may be useful in higher grade tumors. Peptide receptor-targeted radionuclide therapy may be of benefit and is mostly used after medical therapies fail. However, it is considered an investigational modality. More recently, targeted drugs such as mammalian target of rapamycin (mTOR) inhibitors and anti-angiogenics have been investigated. Objective remissions are rare. Their value remains to be rigorously elucidated. Increased efficacy requires a better understanding of the underlying tumor biology and identification of molecular pathological criteria to allow appropriate preselection of candidates for targeted therapies.

Sunitinib malate for the treatment of pancreas malignancies--where does it fit?

INTRODUCTION

Sunitinib , a broad-spectrum multikinase inhibitor, was recently approved for use in progressive, well-differentiated pancreatic neuroendocrine tumors (pNETs). Its mechanism of action affects various signaling cascades involving antiangiogenesis and tumor proliferation, including vascular endothelial growth factors and platelet-derived growth factors.

AREAS COVERED

In this article, we review sunitinib's mechanism of action at a molecular level and review key preclinical and clinical studies for pNETs and more limited data regarding sunitinib's evaluation in pancreas adenocarcinoma. The data for sunitinib in pNETs are placed in the context of the changing landscape of therapeutic options for this cancer, and relevant ongoing clinical trials and future directions are highlighted.

EXPERT OPINION

Sunitinib malate has become integrated into routine clinical management for pNETs; however, its role in pancreas adenocarcinoma is not established.

Translation of molecular pathways into clinical trials of neuroendocrine tumors

Current treatment options for neuroendocrine tumors (NET) include somatostatin analogs, interferon-α, peptide receptor-targeted therapy and cytotoxic chemotherapy. Most patients undergo sequential therapies since these drugs are active only in subpopulations of patients and for a limited period of time. There is a need for novel drugs that are capable of amelioration of symptomatology (syndromic control) and/or tumor growth control. A number of diverse signaling pathways are involved in the pathogenesis of NET and tumor growth, thus many potential targets are available for drug targeting. Targeted therapies therefore represent an appropriate developmental therapeutic strategy given the multiplicity of potential targets in NET. These include but are not limited to: inhibitory or activating G protein-coupled receptors, receptor tyrosine kinases, ligands, and intracellular targets such as the mammalian target of rapamycin (mTOR). Numerous drugs that utilize single or multiple targets are currently in clinical development. Recently, two target-directed agents, the multiple tyrosine kinase inhibitor sunitinib and the mTOR inhibitor everolimus, have been approved for the treatment of progressive pancreatic NET. This review provides a broad overview of established and potential molecular targets in NET, summarizes data from phase II and III clinical trials with targeted drugs and outlines future therapeutic directions.

Angiogenesis in neuroendocrine tumors: therapeutic applications

The considerable research efforts devoted to the understanding of the mechanisms of tumor angiogenesis have resulted in the development of targeted anti-angiogenic therapies and finally in their introduction in clinical practice. Neuroendocrine tumors (NETs), which are characterized by a high vascular supply and a strong expression of VEGF-A, one of the most potent pro-angiogenic factors, are an attractive indication for these new treatments. However, several lines of evidence show that the dense vascular networks associated with low-grade NETs are more likely to be a marker of differentiation than a marker of aggressiveness, as in other epithelial tumors. These observations form the basis for the so-called 'neuroendocrine paradox', according to which the most vascularized are the most differentiated and the less angiogenic NETs. This must be kept in mind when discussing the role of anti-angiogenic strategies in the treatment of NETs. Nevertheless, several targeted therapies, with direct or indirect anti-angiogenic properties, including anti-VEGF antibodies, tyrosine kinase inhibitors (sunitinib) and mTOR inhibitors (everolimus), have recently proven to be of clinical benefit. In addition, some drugs already used in NET treatment, such as somatostatin analogues and interferon-α, may also have anti-angiogenic properties. The main challenges for the next future are to validate biomarkers for the selection of patients and the prediction of their response to refine the indications of anti-angiogenic targeted therapies and to overcome the mechanisms of resistance, which explain the limited duration of action of most of these treatments.

Phase II trial of capecitabine combined with thalidomide in second-line treatment of advanced pancreatic cancer

BACKGROUND

To evaluate the efficacy and tolerability of capecitabine combined with thalidomide in patients with advanced pancreatic cancer (APC) who have previously received gemcitabine-based therapy.

METHODS

A total of 31 patients were recruited prospectively in Shandong Tumor Hospital from May 2007 to April 2009. Capecitabine was offered to patients twice a day at a dose of 1250 mg/m(2) for 14-day then followed by 7-day rest. Thalidomide was administered 100 mg/day without interruption until disease progression or occurrence of unacceptable toxicity.

RESULTS

Two patients presented partial response (PR), 11 patients showed stable disease (SD) and eighteen patients presented progressive disease (PD). The median progression-free survival (PFS) was 2.7 months (95% confidence interval (CI), 2.4-3.3) and the median overall survival (OS) was 6.1 months (95% CI, 5.3-6.9). In the subgroup analysis, PFS had a significant difference between the serum CA19-9 level decreasing >25% and decreasing <25%, with 3.0 months (95% CI, 2.5-3.6) and 2.5 months (95% CI, 1.8-3.2), (Log Rank = 0.02), respectively. Hematological toxicity included leukocytopenia, anemia and neutropenia. Non-hematological toxicities included diarrhea, skin rash, nausea/vomiting, hand-foot syndrome, fatigue, dizziness, drowsiness and constipation.

CONCLUSION

Capecitabine combined with thalidomide is a well-tolerated second-line regimen, in patients with APC refractory to gemcitabine.

Pancreatic neuroendocrine and carcinoid tumors: what's new, what's old, and what's different?

Well-differentiated neuroendocrine tumors (NETs) can be subdivided into carcinoid and pancreatic NETs (panNETs). Recently, two therapies have been FDA approved for progressive well-differentiated pancreatic NETs but have not been submitted for use in carcinoid tumors (Yao, Shah, Ito, et al. N Engl J Med 364:514-23, 2011••; Raymond, Dahan, Raoul, et al. N Engl J Med 364:501-13, 2011••). The first is sunitinib (Sutent(®), Pfizer, Inc.), an orally administered, multitargeted receptor kinase inhibitor. The second targeted agent is everolimus (Afinitor(®), Novartis Pharmaceuticals), a mammalian target of rapamycin (mTOR) inhibitor (Yao, Shah, Ito, et al. N Engl J Med 364:514-23, 2011••). Both agents demonstrated improved progression-free survival but can also result in non-trivial toxicities and therefore, should only be considered in patients with progressing or symptomatic pancreatic NET. This review will discuss "new" NET therapies and provides an overview of liver directed and "older" cytotoxic treatment options. We also briefly outline "what's different" by describing a recent genetics report identifying genetic mutations in panNETs. Such a discovery could potentially be used to stratify treatment and such studies are currently being investigated.

Current status and perspectives of targeted therapy in well-differentiated neuroendocrine tumors

Although neuroendocrine tumors (NET) are a relatively rare malignancy, the reported incidence is increasing, and some of the current treatment options are limited in their efficacy. Standard first-line therapy for metastatic small bowel NET includes somatostatin analogs. Although these agents can provide symptom relief and can delay disease progression in many patients, ultimately, new treatments are required for patients with progressive disease. In recent years, there has been considerable interest in developing agents specifically targeted against some of the pathways known to be involved in cancer cell growth, survival and invasion. In 2011, the mammalian target of rapamycin (mTOR) inhibitor everolimus and the tyrosine kinase inhibitor sunitinib were approved for the treatment of pancreatic NET. Clinical trials evaluating novel targeted agents are ongoing, both as single agents and in combination regimens. We review the current clinical status of these potential new treatments and highlight those with particular promise for the management of well-differentiated NET.

Relevance of angiogenesis in neuroendocrine tumors

While traditional cytotoxic drugs have shown limited efficacy in neuroendocrine tumors (NETs), their biological features have been characterized and can be exploited therapeutically. Their most prominent trait is an extraordinary vascularization in low-grade NETs and an hypoxia-dependent angiogenesis in high-grade NETs, which is associated to a significant expression of many proangiogenic molecules. Therefore, several antiangiogenic compounds have been tested in these malignancies, and among these, sunitinib has demonstrated activity in pancreatic NET patients by dually targeting the VEGFR and PDGFR pathways. In spite of these efficacious clinical results, apparent resistance to antiangiogenic therapies has been described in NET animal models and in clinical trials. Therefore, overcoming antiangiogenic resistance is a crucial step in the subsequent development of antiangiogenic therapies. Several strategies have been postulated to fight resistance, but preclinical studies and clinical trials will investigate and address these therapeutic approaches in the coming years in order to overcome resistance to antiangiogenic therapies in NETs.

New treatment strategies in advanced neuroendocrine tumours

Malignant well-differentiated neuroendocrine tumours of the pancreas and the gastrointestinal tract are rare and clinically challenging heterogeneous neoplasms. This review focuses on neuroendocrine tumours grade 1 and grade 2 (new WHO classification 2010), in comparison to the neuroendocrine tumours grade 3 group, corresponding to poorly differentiated neuroendocrine carcinomas. Surgical resection of the primary and metastases remains the only curative treatment, however many patients with neuroendocrine tumours are diagnosed once unresectable metastases have occurred; management of functioning syndromes with somatostatin analogues remains the priority. Pasireotide, a new somatostatin analogue, is currently undergoing evaluation for carcinoid syndrome. Treatment options for advanced neuroendocrine tumours differ from pancreatic gastrointestinal tract neuroendocrine tumours: (a) in pancreatic neuroendocrine tumours, streptozotocin-based chemotherapies are challenged by other cytotoxic agents (dacarbazine, temozolomide and oxaliplatin); two randomized, placebo-controlled phase III studies have demonstrated that everolimus and sunitinib significantly improved progression-free-survival; (b) in midgut neuroendocrine tumours, octreotide improved time-to-progression in patients with a low proliferation index and low liver burden; preliminary data suggesting efficacy of bevacizumab are still to be confirmed; the effect of everolimus associated with octreotide was almost significant on progression-free-survival in a phase III trial. Liver-directed therapies are effective in both tumour types. New techniques of embolization need further evaluation and must be formally compared to other therapies. Finally, peptide receptor radionuclide therapy has shown promising activity in non-comparative studies in advanced neuroendocrine tumours.

Novel medical therapies of recurrent and metastatic gastroenteropancreatic neuroendocrine tumors

Neuroendocrine tumors (NETs) of the gastrointestinal tract and pancreas are slow-growing but commonly advanced malignancies with increasing incidence and prevalence. While locoregional disease can be effectively managed with resection, treatment of recurrent, progressive or metastatic disease has until recently been limited to palliative embolization and cytoreducitve surgery, with cytotoxic chemotherapeutic agents being the last resort. However, novel molecular targeted therapies inhibiting malignant cell proliferation and neoangiogenesis, as well as new cytotoxic chemotherapy drugs and somatostatin analogues, are all being investigated for their potential use in advanced neuroendocrine tumors. Long-acting release forms of octreotide have been shown to not only improve symptoms in carcinoid syndrome but to also delay progression of gastrointestinal NETs. On the other hand, phase III trials have demonstrated everolimus (with octreotide) and sunitinib to increase progression-free survival in pancreatic NETs. Use of bevacizumab has also shown promise in a phase II study, and results of an ongoing phase III trial comparing it to interferon are eagerly expected. Use of radiolabeled somatostatin analogues is still under investigation, though several phase II studies are encouraging. New cytotoxic agents, most notably temozolomide and capecitabine, are already in use, but their relative effectiveness compared to streptozocin in pancreatic NETs is yet to be determined.

Emerging therapies for advanced gastroenteropancreatic neuroendocrine tumors

Neuroendocrine tumors comprise a heterogeneous group of neoplasms derived from peptide- and amine-producing cells of the neuroendocrine system. Gastroenteropancreatic NET are differentiated into tumors and carcinomas based on their malignant potential and subdivided into those arising from the pancreas (islet cell tumors or pancreatic NET) and the more classical gut "carcinoids". Moderate to well differentiated NET have historically been considered rare tumors but recent epidemiological statistics suggest that their frequency has increased substantially over the past three decades. While the incidence of NET is increasing, data from both the US and UK demonstrate no improvement in outcomes over a similar time period. Due to the generally indolent biology of NET, most patients present with advanced disease before symptoms become apparent. In patients with localized NET, the 5-year survival rates after resection range from 60 to 90%, while regional lymph node involvement decreases the 5-year survival rates after surgery to 50-75%. Patients with distant metastases have a 5 year survival rate of approximately 25-40%. Conventional cytotoxic chemotherapy is of unclear benefit in patients with these generally slow growing tumors. Multiple agents have been tested in Phase 2 and Phase 3 trials. In general, the lack of major objective responses with significant toxicities has limited routine use of traditional chemotherapy agents and has emphasized the need to develop new agents in these diseases. This review will focus on emerging molecularly-targeted treatments with an emphasis on their underlying biologic and preclinical rationale.

Well-differentiated neuroendocrine tumors: a review covering basic principles to loco-regional and targeted therapies

Neuroendocrine tumors (NETs) are a complex group of malignancies with variable prognosis and response to treatment. For pancreatic neuroendocrine and carcinoid tumors, traditional cytotoxic chemotherapies have demonstrated minimal activity. Current approaches for treatment of metastatic disease use a combination of loco-regional and targeted biological therapies. Clinical trials remain critical for evaluation of new and promising therapeutic options for patients with NETs.

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.

New pharmacologic therapies for gastroenteropancreatic neuroendocrine tumors

Successful treatment of unresectable and metastatic gastroenteropancreatic neuroendocrine tumors (GEP-NETs) requires the thoughtful choice of systemic therapy as a component of a multidisciplinary therapeutic approach. The role of somatostatin analogues is established in symptom relief, but the efficacy of interferon and radiopeptide targeted therapy is not clear. The utility of a variety of tyrosine kinase and antiangiogenic agents is variable and under investigation, whereas the role of cytotoxic chemotherapy in poorly differentiated GEP-NETs is accepted. Overall, the ideal treatment of more indolent tumors is less certain. Reassessments of the GEP-NET pathology classification has provided improved logic for the role of a variety of agents, whereas the precise positioning of many new agents that target molecular pathways of angiogenesis and proliferation is under examination. This article describes the current options for systemic therapy for GEP-NETs within the framework of the current World Health Organization classification system.

Effects of T-type calcium channel blockers and thalidomide on contractions of rat vas deferens

BACKGROUND AND PURPOSE

In rat vas deferens, nerve mediated-contractions to a single electrical stimulus consist of an early purinergic and a later adrenergic component with differing sensitivities to L-type calcium channel blockers. We have investigated the effects of the T-type calcium channel blockers mibefradil and (1S, 2S)-2-[2-[[3-(1H-benzimidazol-2-yl)propyl]methylamino]ethyl]-6-fluoro-1,2,3,4-tetrahydro-1-(1-methylethyl)-2-naphthalenyl cyclopropanecarboxylic dihydrochloride (NNC 55-0396) against contractions in rat vas deferens. In addition, the actions of thalidomide were examined.

EXPERIMENTAL APPROACH

Prostatic and epididymal portions of rat vas deferens were stimulated with a single electrical stimulus every 5 min, and mouse whole vas deferens was stimulated with 40 pulses at 10 Hz every 5 min.

KEY RESULTS

Both mibefradil and NNC 55-0396 (100 microM) produced inhibition of contractions of epididymal portions (42 +/- 13%, n= 7, and 43 +/- 4%, n= 15, of control respectively). However, both agents produced small inhibitions of responses in prostatic portions, presumably by L-type calcium channel block. Thalidomide (100 microM) inhibited contractions in epididymal (55 +/- 4% of control, n= 17) but not in prostatic portions of rat vas deferens. Thalidomide (10-100 microM) also inhibited contractions in mouse vas deferens.

CONCLUSIONS AND IMPLICATIONS

The T-type calcium channel blockers mibefradil and NNC 55-0396 block particularly the adrenoceptor-mediated, nifedipine-resistant response to nerve stimulation in rat vas deferens, and this may suggest that this component involves T-type calcium channels. In addition, thalidomide has actions that resemble those of the T-type calcium channel blockers, in that it blocks nifedipine-resistant contractions in epididymal portions.

Angiopoietin-2 promotes disease progression of neuroendocrine tumors

PURPOSE

Inhibition of angiogenesis represents a promising therapeutic strategy in neuroendocrine tumors. Angiopoietin-2 (Ang-2), a ligand of the endothelial tyrosine kinase Tie-2, is emerging as a key regulator of vascular remodeling during tumor angiogenesis. We therefore addressed the expression and biological significance of Ang-2 in human neuroendocrine tumors.

EXPERIMENTAL DESIGN

Surgical specimens and serum from neuroendocrine tumor patients were used to determine Ang-2 expression by in situ hybridization or ELISA (circulating Ang-2). Ang-2 biological effects were evaluated following stable transfection into BON human pancreatic neuroendocrine tumor cells. BON clones were grown as orthotopic xenografts in nude mice to determine tumor growth and abdominal metastatic spread. Further analyses included microvessel density, lymphatic vessel density, and nodal invasion.

RESULTS

Specimens from pancreatic neuroendocrine tumors and nontransformed pancreatic tissue revealed uniform expression of Ang-2 mRNA in endothelial cells. In contrast, epithelial expression of Ang-2 mRNA occurred exclusively in neuroendocrine tumors. Overexpression of Ang-2 in BON orthotopic xenografts did not affect primary tumor growth, although successful Ang-2 induction was confirmed from elevated serum levels. However, increased microvessel density and enhanced lymphatic metastasis were evident in Ang-2-expressing tumors, indicating a functional role of Ang-2 in experimental neuroendocrine tumors. Consistent with this notion, circulating Ang-2 was significantly elevated in neuroendocrine tumor patients compared with healthy controls. Circulating Ang-2 furthermore correlated with metastatic versus localized disease. The highest Ang-2 concentrations occurred in patients with liver metastasis, and concentrations >or=75th percentile predicted shorter survival (P = 0.0003).

CONCLUSION

Induction of Ang-2 in neuroendocrine tumors represents a clinically relevant pathomechanism of disease progression and constitutes an adverse prognostic marker.

Review article: future therapies for management of metastatic gastroenteropancreatic neuroendocrine tumours

BACKGROUND

Gastroenteropancreatic neuroendocrine tumours (GEP NETs) are relatively uncommon tumours that occur anywhere within the gastrointestinal tract. The prevalence of GEP NETs is estimated to be 35 per 100 000 population. Patients often present with metastatic disease and consequently, palliative treatments form the mainstay of therapy.

AIM

To review the current and novel therapeutic options for management of GEP NETs.

METHODS

Searches for all studies related to GEP NETs, NETs and carcinoid tumours in Medline and abstracts from international meetings.

RESULTS

Somatostatin analogues remain the first line therapy for management of symptoms of GEP NETs and may have anti-proliferative action. New somatostatin analogues with different somatostatin receptor affinity have been developed. Radionuclide peptide receptor therapy is established in patients with positive somatostatin scintigraphy. A number of new agents and targeted therapies are currently being evaluated in a phase I and II studies and these include angiogenic inhibitors, mammalian target of rapamycin inhibitors and immune therapies.

CONCLUSIONS

A number of nonsurgical therapies are available for management of gastroenteropancreatic neuroendocrine tumours. It is hoped, the development of some of these promising novel therapies will expand the therapeutic armamentarium.

Treatment of advanced disease in patients with well-differentiated neuroendocrine tumors

Well-differentiated neuroendocrine tumors (NETs), which are also referred to as well-differentiated endocrine carcinoma according to WHO terminology, are usually slow-growing cancers, even when they exhibit gross local invasion and/or metastases. The survival of patients with metastatic NET is often measured in years to decades. Once NET progresses or becomes symptomatic the patient's prognosis is poor. An important challenge for clinicians is to distinguish at an early stage those patients who will die with the disease, from those who will succumb because of it, so that the appropriate level of care can be administered. Reliable genomic predictors could provide substantial advancements in prognosis and, possibly, treatment; however, such markers are currently unavailable. Early literature on the treatment of NETs is confounded by a lack of formal objective response criteria. Somatostatin analogs can control symptoms and can stabilize some slow-growing tumors, but rarely result in tumor regression. Surgery is curative in only a minority of patients, and systemic chemotherapy is minimally effective. Advances in the understanding of tumor biology have led to the identification of important cellular processes involved in the pathogenesis of NETs, and agents that target these processes have now entered clinical trials. We will discuss the data on therapies currently used to treat well-differentiated NETs, and the strategies being used in clinical trials.

Repeat transarterial chemoembolization (TACE) for progressive hepatic carcinoid metastases provides results similar to first TACE

BACKGROUND

Transarterial chemoembolization (TACE) is commonly used to treat metastatic carcinoid tumors; however, the management of progressive disease is less clear. We sought to determine if patients with disease progression after TACE would benefit from repeat TACE.

METHODS

The records of 27 patients undergoing repeat TACE for radiologic or symptomatic progression after TACE for metastatic carcinoid were reviewed and compared to 122 undergoing first TACE. Overall and progression-free survivals were estimated by the Kaplan-Meier method.

RESULTS

Mean disease-free interval after first TACE was 11.8 months. Radiologic response was observed in 61% compared to 82% after first TACE (p=0.058); hormone response in 64% compared to 80% (p=0.159); and symptomatic response in 77% compared to 92% (p=0.053). The complication rate after repeat TACE was lower than after first TACE (p=0.03). Median overall survival was similar after repeat (28.1 months) and first TACE (33.3 months) (p=0.53). Progression-free survival was shorter after repeat TACE but not significantly so. No factor examined could predict survival after repeat TACE.

CONCLUSION

Repeat TACE for patients with hepatic carcinoid metastases failing first TACE or having evidence of disease progression is safe and offers a viable treatment option.