Everolimus plus octreotide long-acting repeatable for the treatment of advanced neuroendocrine tumours associated with carcinoid syndrome (RADIANT-2): a randomised, placebo-controlled, phase 3 study

[Neuroendocrine tumors: the age of targeted therapies]

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are the second most prevalent group of advanced gastrointestinal tract tumors. Resources invested in research on this patient population have exponentially increased in recent years, and this has become one of the most attractive fields for oncological research. Several proangiogenic proteins have been found to be overexpressed in GEP-NETs, including vascular endothelial growth factor and its receptors and the more closely related intracellular signaling pathways such as the epidermal growth factor pathway, type I insulin-like growth factor receptor, and the PI3K-(PTEN)-AKT-mTOR pathway. The recent results of the three most important Phase III studies in GEP-NETs have allowed for approval of two targeted agents, sunitinib and everolimus, for the treatment of patients with pancreatic neuroendocrine tumors after decades of minimal advances in this population.

Therapy innovation for the treatment of pancreatic neuroendocrine tumors

INTRODUCTION

Traditional therapeutic approaches for patients with advanced neuroendocrine tumors (NETs) have included treatment with somatostatin analogs, hepatic-directed therapies, interferon and cytotoxic chemotherapy. Current knowledge about biological behavior of pancreatic neuroendocrine tumors (pNETs) has increased in the last decade, and some studies have been conducted to translate in the clinical setting. Among several molecular agents investigated in patients with progressive pNETs, everolimus and sunitinib have been studied in large Phase III trials. Both have produced significant benefit, with improvement in progression-free survival. These results were published last year by NEJM and were updated at the ASCO Annual Meeting in June 2011.

AREAS COVERED

This review focuses on the potential molecular targets in pancreatic NETs in the light of recent advances. Furthermore, it summarizes the available data for targeted agents from Phase II and III trials open to patients with this tumor.

EXPERT OPINION

These new agents are likely to play an increasingly important role in the future management of advanced pNETs. Their use in earlier phases of the disease could improve clinical outcome, avoiding side effects of the more toxic chemotherapy. The challenge in medical treatment of pNET is to define the patients who can benefit from this innovative therapy; future research should be directed to find predictive markers for response to the targeted agent.

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.

[Medicinal therapy of metastasized neuroendocrine tumors of the gastroenteropancreatic system.]

Neuroendocrine neoplasms of the gastroenteropancreatic system are classified according to the WHO classification system 2010 into neuroendocrine tumors (NET) and neuroendocrine carcinomas (NEC). The proliferation index Ki-67 and the grading of NETs is essential for the prognosis and therapy plan. Also NET tumor biology and therapeutic options may differ depending on the primary NET tumor location. Palliative therapy of inoperable NETs involves local ablative methods in cases of primary liver metastasis, peptide receptor radionuclide therapy (PRRT) in NETs expressing somatostatin receptors and different options for medicinal therapy. This manuscript reviews the current role of biotherapy with somatostatin analogues and interferon-alpha for symptom and tumor control. In addition conventional chemotherapy regimens and novel molecular targeted therapeutic options, such as sunitinib or everolimus in NET of the pancreas are reviewed. Possible therapeutic algorithms are discussed.

Emerging therapeutic options for advanced enteropancreatic neuroendocrine tumors

INTRODUCTION

Several chemotherapy agents and combinations have proven effective in the therapy of advanced enteropancreatic neuroendocrine tumors (EP-NETs). However, their toxicity can be significant. Recent understanding of the molecular mechanisms of these tumors, especially the central role of tumor angiogenesis, has led to the identification of new therapeutic targets and agents directed at the molecular level.

AREAS COVERED

This paper gives a comprehensive evaluation of the existing therapeutic armamentarium for EP-NETs. Narrated in a historical perspective, this review analyzes the available information on traditional chemotherapy agents, interferon-α and somatostatin analogs, as well as newer therapies and experimental agents.

EXPERT OPINION

Despite recent advances, a curative approach for metastatic EP-NETs is yet to be discovered. To date, sunitinib and everolimus have been shown to impact progression-free survival only in pancreatic NETs, and the duration of this benefit has not yet been established. Further research is necessary to determine whether a combination of these drugs, either together or with other therapies, may yield superior outcomes. Moreover, sequential use of these agents should be explored in an attempt to improve survival. Efficacy of a variety of experimental agents is also being tested in clinical trials.

Safety and efficacy of everolimus in adult patients with neuroendocrine tumors

Neuroendocrine tumors (NETs) consist of a diverse family of tumors which are derived from the neuroendocrine system. Most NETs are well or moderately differentiated tumors with a relatively indolent growth pattern. However, these tumors can cause significant clinical disease due to release of functional products that mediate the carcinoid syndrome and other diverse sequela. They also can grow progressively and cause symptoms from local invasion or distant metastasis. NETs are optimally treated with surgery and somatosatin analogs (SSA’s) to control symptoms but are relatively insensitive to systemic chemotherapy. As a result, patients with advanced unresectable NETs have a poor prognosis. In 2011, two targeted therapies, sunitinib and everolimus were approved in the subset of progressive pancreatic NETs (pNETs). Everolimus is an oral inhibitor of the growth stimulatory mTOR pathway. In Phase 2 trials in NETs and pNETs, everolimus was well tolerated and associated with some response and widespread disease stabilization. In follow-up, randomized Phase 3 trials, everolimus was compared to placebo. In the RADIANT-2 trial, everolimus and a somatostatin analog were used in patients with functional NETs and treatment was associated with an an improvement in progression-free survival (PFS). In the RADIANT-3 trial, patients with pNET were randomized to receive everolimus or placebo along with best supportive care. Everolimus was again associated with improvement in PFS compared to placebo and it has been approved by the FDA for patients with progressive pNET. Everolimus is associated with frequent low grade toxicity but is also notable for increased rates of infection as well as non-infectious pneumonitis. mTOR inhibition with everolimus represents a significant advance in the treatment of advanced neuroendocrine tumors.

Quality of clinical trials in gastroenteropancreatic neuroendocrine tumours

BACKGROUND

The heterogeneity of neuroendocrine tumours (NETs) makes interpretation of clinical trials in this disease challenging. Our aim was to review the quality of treatment trials in NETs in order to inform the design and reporting of future studies.

METHODS

We identified studies by searching MEDLINE. We considered all phase II and III trials of systemic antineoplastic treatments published between 2000 and 2011. Information on trial design, study population, end points, statistical considerations and results was abstracted from each article using a standardized form.

RESULTS

Seven phase III and 39 phase II trials were identified. The make-up of the study population was variable: only 24% of trials included patients with one type of tumour (pancreatic NET or carcinoid tumour), 41% included patients with both tumour types, and 35% of trials included other endocrine cancers. Disease progression at baseline was often not reported and was documented for all patients in 22% of the trials. The functional status of the tumour, tumour differentiation, and Ki67 index were reported in 35, 43, and 15% of trials, respectively. The primary end point was clearly defined in 72% of trials. Identifiable statistical design, and predefined sample size were reported in 74 and 61% of trials, respectively. Conflicts of interest and study sponsorship were reported in 46 and 85% of trials.

CONCLUSIONS

The quality of the design and reporting of phase II/III NET trials, as described in other cancers, is poor. Future trials should include more homogenous patient populations while adhering to rigorous selection, reporting and interpretation of population and trial parameters.

Hepatic arterial embolization versus chemoembolization in the treatment of liver metastases from well-differentiated midgut endocrine tumors: a prospective randomized study

BACKGROUND

Liver surgery is the best treatment for endocrine liver metastases, but it is often impossible due to diffuse disease. Systemic chemotherapy is poorly effective. Hepatic arterial embolization (HAE) and chemoembolization (HACE) have shown efficacy but have never been compared.

PATIENTS AND METHODS

Patients with progressive unresectable liver metastases from midgut endocrine tumors were randomly assigned to receive HAE or HACE (two procedures at 3-month interval). The primary end point was the 2-year progression-free survival (PFS) rate. Secondary end points were response rates, overall survival, and safety.

RESULTS

Twelve patients were assigned to receive HACE and 14 to receive HAE. The patient characteristics were well matched across the treatment arms. The 2-year PFS rates were 38 and 44% in the HACE and HAE arms, respectively (p = 0.90). Age, gender, previous resection of the primary tumor or liver metastases, extent of liver involvement, and concomitant treatment with somatostatin analogues were not associated with changes in PFS, whereas elevated baseline urinary 5-HIAA and serum chromogranin A levels were associated with shorter PFS. The 2-year overall survival rates were 80 and 100% in the HACE and HAE arms, respectively (p = 0.16). The disease control rate on CT scan was 95%. Grade 3 toxicity occurred in 19% of patients, with no treatment-related deaths and no differences in the treatment arms.

CONCLUSION

HACE and HAE are safe and permit tumor control in 95% of patients with progressive liver metastases from midgut endocrine tumors. The 2-year PFS was not higher among patients receiving HACE, not favoring the hypothesis of an additive efficacy of arterial chemotherapy or embolization alone.

Treatment of neuroendocrine tumor liver metastases

In the care of patients with hepatic neuroendocrine metastases, medical oncologists should work in multidisciplinary fashion with surgeons, interventional radiologists, and radiation oncologists to assess the potential utility of liver-directed and systemic therapies. This paper addresses the various roles and evidence basis for cytoreductive surgery, thermal ablation (radiofrequency, microwave, and cryoablation), and embolization (bland embolization (HAE), chemoembolization (HACE), and radioembolization) as liver-directed therapies. Somatostatin analogues, cytotoxic chemotherapy, and the newer agents everolimus and suntinib are discussed as a means for controlling intra- and extrahepatic disease, along with peptide receptor radiotherapy (PRRT). Finally, the experience with orthotopic liver transplant for neuroendocrine tumors is described.