Evolving diagnostic and treatment strategies for pancreatic neuroendocrine tumors

Increased CDC20 expression is associated with pancreatic ductal adenocarcinoma differentiation and progression

Purpose

Cell division cycle 20 (CDC20) homolog is an anaphase-promoting complex activator that is essential for cell division, but whether its expression in pancreatic ductal adenocarcinoma (PDAC) is significant is unknown. In this retrospective study, we determined whether aberrant CDC20 expression can be used as a biomarker in pancreatic ductal adenocarcinoma (PDAC) tumorigenesis and whether its expression reflects clinical progression.

Experimental design

We compared CDC20 expression levels in normal, cancerous, and inflamed pancreatic tissues from stage II PDAC patients with clinical outcomes and determined CDC20 levels in seven PDAC cell lines. CDC20 was identified using a cDNA microarray database containing gene expression profiles for PDAC tissues and cell lines and chronic pancreatitis and normal pancreas tissues. Its expression was confirmed by real-time quantitative reverse-transcriptase-polymerase chain reaction (qRT-PCR). An immunohistochemical analysis of tissue microarrays from resected PDAC tumors and paired benign pancreatic tissues was done and CDC20 levels were correlated with clinical outcome.

Results

Fifty-six patients were included in this study. A microarray analysis revealed 5-fold higher CDC20 expression in PDAC tissue than in chronic pancreatitis tissue. A qRT-PCR analysis confirmed a mean 20-fold higher CDC20 level in PDAC tissue than in normal pancreas and pancreatitis tissue. RNA and protein CDC20 expression was detected in several PDAC cell lines. An immunohistochemical analysis revealed higher CDC20 protein expression levels in PDAC tissue than in normal pancreas tissue, and high CDC20 expression was associated with poor differentiation (P = 0.020) and a significantly lower 5-year recurrence-free survival rate (P = 0.039); we also found a trend toward a shorter overall survival duration.

Conclusions

Aberrant CDC20 expression may play an important role in PDAC tumorigenesis and progression and may thus be useful as a marker of disease progression and prognosis and as a therapeutic target.

Laparoscopic surgical exploration is an effective strategy for locating occult primary neuroendocrine tumors

BACKGROUND

Many patients with neuroendocrine tumors (NETs) have metastases at diagnosis. Despite extensive metastases the primary tumors remain small and difficult to locate.

METHODS

Records of patients diagnosed with metastatic abdominal NETs from 2006 to 2010 were reviewed retrospectively. Results of preoperative imaging, procedures, and surgical explorations were compared for their efficacy at finding primary tumors.

RESULTS

Sixty-three patients were identified. Seventeen percent (11 of 63) of tumors were located by preoperative testing. The sensitivities of preoperative colonoscopy (23% [n = 26]), computed tomography scan (6.7% [n = 60]), and somatostatin receptor scintigraphy (2.0% [n = 52]) were low. No tumors were found by magnetic resonance imaging (n = 9), upper endoscopy (n = 24), capsule endoscopy (n = 2), or bronchoscopy (n = 4). Surgical exploration was the most sensitive (79% [n = 63]) method of tumor detection. Seventy-two percent of surgical localizations were laparoscopic.

CONCLUSIONS

Surgical exploration was superior to all other modalities for locating primary NETs. Laparoscopy had a high probability of finding occult primary neuroendocrine tumors.

Neuroendocrine tumors of the pancreas

PURPOSE OF REVIEW

Pancreatic neuroendocrine tumors (PNETs) are rare tumors, with an incidence of one per 100, 000 individuals per year, and they account for 1-2% of all pancreatic neoplasms. PNETs are a heterogeneous group with varying clinical presentation, tumor biology and prognosis. This article reviews the current diagnostic strategy and treatment armamentarium for PNETs. Special attention is paid to recent and ongoing developments in treatment, particularly with regards to multimodality treatment and newer systemic therapies for unresectable disease.

RECENT FINDINGS

There has been significant progress in the genetic understanding of hereditary syndromes in regards to PNETs, as well as in the diagnosis and treatment of resectable and nonresectable PNETs. Whereas surgical therapy remains the most advisable therapy for resectable neuroendocrine tumors of the pancreas, there have been significant recent advances in systemic therapy for those with unresectable disease. Results from recent clinical trials examining mammalian target of rapamycin inhibitors and tyrosine kinase inhibitors for unresectable disease are promising in expanding treatment options for metastatic PNETs.

SUMMARY

Neuroendocrine tumors of the pancreas are a heterogeneous group of tumors with varying clinical presentation, tumor biology and prognosis. Clinicians must be aware of the variety of manifestations of this disease, as well as the role of systemic chemotherapy in treatment of unresectable disease.

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.

Gastroenteropancreatic neuroendocrine tumors: new insights in the diagnosis and therapy

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

Hepatic arterial embolization for the treatment of metastatic neuroendocrine tumors

Neuroendocrine tumors (NETs) have a high predilection for metastasizing to the liver and can cause severe debilitating symptoms adversely affecting quality of life. Although surgery remains the treatment of choice, many liver metastases are inoperable at presentation. Hepatic arterial embolization procedures take advantage of the arterial supply of NET metastases. The goals of these therapies are twofold: to increase overall survival by stabilizing tumor growth, and to reduce the morbidity in symptomatic patients. Patients treated with hepatic arterial embolization demonstrate longer progression-free survival and have 5-year survival rates of nearly 30%. The safety of repeat embolizations has also been proven in the setting of recurrent symptoms or progression of the disease. Despite not being curative, hepatic arterial embolization should be used in the management of NETs with liver metastases. Long-term survival is not uncommon, making aggressive palliation of symptoms an important component of treatment.