The NANETS consensus guidelines for the diagnosis and management of gastrointestinal neuroendocrine tumors (nets): well-differentiated nets of the distal colon and rectum

Staging of gastroenteropancreatic neuroendocrine tumors: how we do it based on an evidence-based approach

In contrast to other common types of malignant tumors, the vast majority of gastroenteropancreatic neuroendocrine tumors are well differentiated and slowly growing with only a minority showing aggressive behavior. It is important to accurately stage patients radiologically so the correct treatment can be implemented and to improve prognosis. In this article, we critically appraise the current literature in an effort to establish the current role of radiologic imaging in the staging of neuroendocrine tumors. We also discuss our protocol for staging neuroendocrine tumors.

Antitumor effects of somatostatin analogs in neuroendocrine tumors

BACKGROUND

For decades, somatostatin analogs (including octreotide and lanreotide) have been indicated for relief of the symptoms of flushing, diarrhea, and wheezing associated with secretory neuroendocrine tumors (NETs). Recently, it has been suggested that somatostatin analogs may provide direct and indirect antitumor effects in secretory and nonsecretory NETs in addition to symptom control in secretory NETs.

METHODS

A systematic review of MEDLINE was conducted to identify studies that investigated the antitumor effects of octreotide or lanreotide for patients with NETs. Additional studies not published in the peer-reviewed literature were identified by searching online abstracts. Results. In all, 17 octreotide trials and 11 lanreotide trials that included antitumor effects were identified. Partial response rates were between 0% and 31%, and stable disease rates were between 15% and 89%. Octreotide was the only somatostatin analog for which results of a phase III, randomized, placebo-controlled clinical trial that investigated antitumor effects were published. After 6 months of treatment in this randomized phase III trial, stable disease was observed in 67% of patients (hazard ratio for time to disease progression: 0.34; 95% confidence interval: 0.20-0.59; p = .000072).

CONCLUSIONS

In addition to symptom control for NETs, the data support an antitumor effect of somatostatin analogs and suggest that they may slow tumor growth. Long-acting repeatable octreotide has been shown to have an antitumor effect in a randomized phase III trial in midgut NETs, whereas results are pending in a corresponding controlled trial with lanreotide for patients with intestinal and pancreatic primary NETs.

Neuroendocrine liver metastases: contributions of endoscopy and surgery to primary tumor search

Neuroendocrine tumors (NETs) are diagnosed with increasing frequency and patients often present with liver metastases at the time of diagnosis. Apart from treatment of the metastases, resection of the primary tumor at an early phase is recommended to prevent complications, although it may be difficult to locate, especially in patients with functionally inactive NETs. Small and multifocal tumors in the jejunum and ileum represent a particular challenge. Primary hepatic neuroendocrine carcinoma is extremely rare and is diagnosed only after exclusion of other primary tumors. Therefore, some uncertainty may remain, as small non-hepatic primary tumors may escape detection. Diagnostic work-up in these patients includes biochemical assays and imaging modalities (also comprising specific techniques of scintigraphy and positron emission tomography). This editorial highlights the contributions of endoscopy and operative exploration to the search for the primary tumor. Besides esophago-gastro-duodenoscopy, endoscopic ultrasonography, colonoscopy and bronchoscopy, special endoscopic techniques such as balloon enteroscopy or capsule endoscopy are used with growing experience. Compared with balloon enteroscopy, capsule endoscopy is non-invasive and better tolerated, but it cannot localize a lesion precisely and does not allow biopsy or removal of lesions. Before proceeding to surgery, a discussion of the findings by a tumor board should be a standard procedure. Improvements in diagnostic tools have created new perspectives for the detection of obscure primary tumors in patients with neuroendocrine liver metastases, and these searches are best coordinated by a multidisciplinary team.

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.

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.

Classification and pathology of gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are composed of cells with a neuroendocrine phenotype. The old and the new WHO classifications distinguish between well-differentiated and poorly differentiated neoplasms. All well-differentiated neoplasms, regardless of whether they behave benignly or develop metastases, will be called neuroendocrine tumours (NETs), and graded G1 (Ki67 <2%) or G2 (Ki67 2-20%). All poorly differentiated neoplasms will be termed neuroendocrine carcinomas (NECs) and graded G3 (Ki67 >20%). To stratify the GEP-NETs and GEP-NECs regarding their prognosis, they are now further classified according to TNM-stage systems that were recently proposed by the European Neuroendocrine Tumour Society (ENETS) and the AJCC/UICC. In the light of these criteria the pathology and biology of the various NETs and NECs of the gastrointestinal tract (including the oesophagus) and the pancreas are reviewed.

Management of early gastrointestinal neuroendocrine neoplasms

Neuroendocrine neoplasms (NENs) of the stomach, duodenum, appendix or rectum that are small (≤ 1 cm) and well differentiated can be considered “early” tumors, since they generally have a (very) good prognosis. In the new WHO classification of 2010, these neoplasms are called neuroendocrine tumors/ carcinoids (NETs), grade (G) 1 or 2, and distinguished from poorly differentiated neuroendocrine carcinomas (NECs), G3. NETs are increasing, with a rise in the age-adjusted incidence in the U.S.A. by about 700 % in the last 35 years. Improved early detection seems to be the main reason for these epidemiological changes. Both the better general availability of endoscopy, and imaging techniques, have led to a shift in the discovery of smaller-sized (≤ 10-20 mm) intestinal NETs/carcinoids and earlier tumor stages at diagnosis. Endoscopic screening is therefore effective in the early diagnosis, not only of colorectal adenocarcinomas, but also of NETs/carcinoids. Endoscopic removal, followed up with endoscopic surveillance is the treatment of choice in NETs/carcinoids of the stomach, duodenum and rectum that are ≤ 10 mm in size, have a low proliferative activity (G1), do not infiltrate the muscular layer and show no angioinvasion. In all the other intestinal NENs, optimal treatment generally needs surgery and/or medical therapy depending on type, biology and stage of the tumor, as well as the individual situation of the patient.

[Neuroendocrine colorectal tumors. Surgical and endoscopic treatment]

The incidence of colorectal neuroendocrine tumors (NETs) is rising in developed countries primarily as a result of increased incidental detection by endoscopy and probably also due to a more adequate diagnosis according to the WHO classification. Less than 1% of colorectal NETs produce serotonin so that such tumors are practically never associated with a hormonal carcinoid syndrome. An exact clinico-pathological staging is of paramount importance for the therapeutic strategy and comprises the classification of the tumor type (well or poorly differentiated) and the assessment of established prognostic risk factors (depth of infiltration, vascular invasion, lymph node and distant metastases). Poorly differentiated colorectal NETs often present in an advanced, metastatic state, where surgical therapy is basically palliative. Well-differentiated tumors larger than 2 cm have a high risk of metastatic spread and should be treated as adenocarcinomas by radical oncological surgical resection. This applies to the majority of colon NETs. Tumors smaller than 1 cm, mainly locacted in the rectum, only rarely metastasize and are usually accessible for endoscopic treatment or transanal local surgery. Tumors between 1 and 2 cm in size have an uncertain prognosis and additional risk factors and co-morbidities of the patient have to be considered for a suitable, multidisciplinary therapeutic decision.

Classification and functions of enteroendocrine cells of the lower gastrointestinal tract

With over thirty different hormones identified as being produced in the gastrointestinal (GI) tract, the gut has been described as 'the largest endocrine organ in the body' (Ann. Oncol., 12, 2003, S63). The classification of these hormones and the cells that produce them, the enteroendocrine cells (EECs), has provided the foundation for digestive physiology. Furthermore, alterations in the composition and function of EEC may influence digestive physiology and thereby associate with GI pathologies. Whilst there is a rapidly increasing body of data on the role and function of EEC in the upper GI tract, there is a less clear-cut understanding of the function of EEC in the lower GI. Nonetheless, their presence and diversity are indicative of a role. This review focuses on the EECs of the lower GI where new evidence also suggests a possible relationship with the development and progression of primary adenocarcinoma.

Neuroendocrine tumors in children and young adults: rare or not so rare

This review focuses on neuroendocrine tumors (NETs) that arise in the diffuse neuroendocrine system; these rare tumors can develop in any organ that has dispersed single endocrine cells, for example, the intestine, or in an organ that has clusters of endocrine cells, for example, pancreatic islets. Previously considered benign, NETs are now recognized to recur locally or metastasize to liver and bone if not completely excised early in their course of development. This article summarizes the epidemiology and reviews the diagnostic and therapeutic challenges of NETs in children and youth, noting especially those NETs that are more prevalent in young people than in older adults.