Several guidelines and standards of care on the management of neuroendocrine tumors (NETs) have been published by expert national and international groups in recent years [1,2,3,4,5,6,7,8,9]; additional changes in how these patients are managed are evolving rapidly, and since the last European Neuroendocrine Tumor Society (ENETS) Guidelines in 2011/12 [8], new important data have become available pertaining to novel diagnostic tools and therapies. On October 30th and 31st, 2014, the ENETS held an Advisory Board meeting in Vienna aiming at critically discussing and updating the ENETS Guidelines on the Diagnosis and Treatment of Neuroendocrine Tumors generated initially in 2005-2006 [2,4] and revised in 2011 [8].

The consensus sessions covered the following neuroendocrine neoplasm-related topics by sites of origin or stage: gastroduodenal, midgut (including appendix), hindgut, functional pancreatic, non-functional pancreatic, and two final sessions that covered liver and other distant metastases from neuroendocrine neoplasms of any origin and a separate session devoted to neuroendocrine high-grade tumors and carcinomas.

The participants at the conference were asked to focus on the relevant literature published between 2011 and 2015. They met over two and a half days, in which data and new evidence were presented. The participants then retreated to break-out sessions according to their disciplines and were required to answer questions listed in a workbook created by the session chairs and the organizing committee. The workbook questions were tailored on the text of the initial guidelines framework [2,4], focusing on the new available evidence. All relevant areas were updated via a thorough literature review and the questions that the chairpersons considered appropriate to discuss the new evidence. All participants were encouraged to challenge the document. Recent data on new evidence and insights were intensely discussed in working-group sessions as well as during the plenary session. Notes were taken continuously, so that the final agreement on each question was noted and returned to each session chair for preparation of the consensus statements. The magnitude of the consensus for each answer was estimated to achieve unanimity. In addition to providing textual guidelines, delegates were requested to elaborate accurate but simple diagnostic and therapeutic algorithms to help practitioners in everyday practice (these will hopefully be accessible via a specific ENETS website link at a future date).

Owing to anticipated results emanating from three important phase III trials in 2015, further new additional data throughout 2015 were incorporated into the consensus achieved at the on-site Vienna meeting via the two chairs of each individual working group, and additional data were presented to the Advisory Board meeting in November 2015 in Brussels to achieve consensus.

The next step was to review the data produced and to transform it into working papers for publication. The Organizing Committee defined a specific protocol, establishing the design of each paper, the tasks for authors, and the general authorship policy. The papers were designed to update the previously published ENETS Guidelines, incorporating the approved consensus statements.

The following seven papers [10,11,12,13,14,15,16] are the significant and tangible result of two Advisory Board Consensus Conference meetings. These ENETS Guidelines provide important updates from world leaders in the field of NETs to compliment former consensus conferences in providing practical clinical evidence for NET patient management. The provision of useful diagnostic and therapy algorithms will also help to simplify everyday clinical practice. All participants equally contributed a great effort, and the delegates generously devoted their time, experience and enthusiasm to building the following Consensus Guidelines. We thank them for their efforts, great dedication and good will. We believe that the following papers will be practical and useful instruments for heath carers in dealing with patients with digestive NETs.

1.
Plöckinger U, Rindi G, Arnold R, Eriksson B, Krenning EP, de Herder WW, Goede A, Caplin M, Oberg K, Reubi JC, Nilsson O, Delle Fave G, Ruszniewski P, Ahlman H, Wiedenmann B: Guidelines for the diagnosis and treatment of neuroendocrine gastrointestinal tumours. A consensus statement on behalf of the European Neuroendocrine Tumour Society (ENETS). Neuroendocrinology 2004;80:394-424.
2.
Rindi G, de Herder WW, O'Toole D, Wiedermann B: ENETS consensus guidelines for the management of digestive neuroendocrine tumors. Neuroendocrinology 2006;84:151-216.
3.
Rindi G, Kloppel G, Alhman H, et al: TNM staging of foregut (neuro)endocrine tumors: a consensus proposal including a grading system. Virchows Arch 2006;449:395-401.
4.
Rindi G, Kloppel G, Couvelard A, et al: TNM staging of midgut and hindgut (neuro)endocrine tumors: a consensus proposal including a grading system. Virchows Arch 2007;451:757-762.
5.
Rindi G, de Herder WW, O'Toole D, Wiedermann B: ENETS consensus guidelines for the management of digestive neuroendocrine tumors: the second event and some final considerations. Neuroendocrinology 2008;87:5-7.
6.
Plöckinger U, Wiedenmann B, de Herder W: ENETS consensus guidelines for the standard of care in neuroendocrine tumors. Neuroendocrinology 2009;90:159-161.
7.
O'Toole D, Rindi G, Plöckinger U, Wiedenmann B: ENETS consensus guidelines for the management of patients with rare metastases from digestive neuroendocrine tumors: rationale and working framework. Introduction. Neuroendocrinology 2010;91:324-325.
8.
Salazar R, Wiedenmann B, Rindi G, Ruszniewski P: ENETS 2011 consensus guidelines for the management of patients with digestive neuroendocrine tumors: an update. Neuroendocrinology 2012;95:71-73.
9.
Kvols LK, Brendtro KL; North American Neuroendocrine Tumor Society (NANETS): The North American Neuroendocrine Tumor Society (NANETS) guidelines: mission, goals, and process. Pancreas 2010;39:705-706.
10.
Delle Fave G, O'Toole D, Sundin A, Taal B, Ferolla P, Ramage JK, Ferone D, Ito T, Weber W, Zheng-Pei Z, De Herder WW, Pascher A, Ruszniewski P; all other Vienna Consensus Conference participants: ENETS consensus guidelines update for gastroduodenal neuroendocrine neoplasms. Neuroendocrinology 2016;103:119-124.
11.
Niederle B, Pape UF, Costa F, Gross D, Kelestimur F, Knigge U, Öberg K, Pavel M, Perren A, Toumpanakis C, O'Connor J, O'Toole D, Krenning E, Reed N, Kianmanesh R; all other Vienna Consensus Conference participants: ENETS consensus guidelines update for neuroendocrine neoplasm of the jejunum and ileum. Neuroendocrinology 2016;103:125-138.
12.
Ramage JK, De Herder WW, Delle Fave G, Ferolla P, Ferone D, Ito T, Ruszniewski P, Sundin A, Weber W, Zheng-Pei Z, Taal B, Pascher A; all other Vienna Consensus Conference participants: ENETS consensus guidelines update for colorectal neuroendocrine neoplasms. Neuroendocrinology 2016;103:139-143.
13.
Pape UF, Niederle B, Costa F, Gross D, Kelestimur F, Kianmanesh R, Knigge U, Öberg K, Pavel M, Perren A, Toumpanakis C, O'Connor J, Krenning E, Reed N, O'Toole D; all other Vienna Consensus Conference participants: ENETS consensus guidelines for neuroendocrine neoplasms of the appendix (excluding goblet cell carcinomas). Neuroendocrinology 2016;103:144-152.
14.
Falconi M, Eriksson B, Kaltsas G, Bartsch DK, Capdevila J, Caplin M, Kos-Kudla B, Kwekkeboom D, Rindi G, Klöppel G, Reed N, Kianmanesh R, Jensen RT; all other Vienna Consensus Conference participants: ENETS consensus guidelines update for the management of patients with functional pancreatic neuroendocrine tumors and non-functional pancreatic neuroendocrine tumors. Neuroendocrinology 2016;103:153-171.
15.
Pavel M, O'Toole D, Costa F, Capdevila J, Gross D, Kianmanesh R, Krenning E, Knigge U, Salazar R, Pape UF, Öberg K; all other Vienna Consensus Conference participants: ENETS consensus guidelines update for the management of patients with distant metastatic disease of intestinal, pancreatic, bronchial neuroendocrine neoplasms (NEN) and NEN of unknown primary site. Neuroendocrinology 2016;103:172-185.
16.
Garcia-Carbonero R, Sorbye H, Baudin E, Raymond E, Wiedenmann B, Niederle B, Sedlackova E, Toumpanakis C, Anlauf M, Cwikla JB, Caplin M, O'Toole D, Perren A; all other Vienna Consensus Conference participants: ENETS consensus guidelines for high-grade gastroenteropancreatic neuroendocrine tumors and neuroendocrine carcinomas. Neuroendocrinology 2016;103:186-194.
2016
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