Small Intestine Neuroendocrine Tumours (SI NETs): To cut or not to cut?

Updated 12th April 2026. New paper from known experts in NET surgery. Definitely worth reading as it covers some areas which are considered controversial but very relevant to the situations than can arise in small intestine NET surgery.

Recent 2026 paper from multiple experts across the world including but not limited to Canada/UK/Europe/Mexico/Israel/USA

“The current recommended approach for all patients with stage IV SI-NETs is for assessment by a multidisciplinary team with NET expertise, including a surgeon, and that strong consideration should be given towards primary tumour resection, even in the absence of recognized symptoms and for patients with unresectable metastatic disease. This is supported by consensus opinion from international NET societies across the world”

Citation. Julie Hallet, Massimo Falconi, Sean Bennet, Andrea Frilling, Alexandra Gangi, Sébastien Gaujoux, Rodney Pommier, Emilio Bertani, Gabriela A Buerba, Jennifer Chan, Callisia N Clarke, Sophie Deguelte, Jaydira Del Rivero, Els Nieveen van Dijkum, Teodora Dumitra, Dilmurodjon Eshmuminov, Anton Engelsman, Francesca Fermi, Simona Grozinsky-Glasberg, James R Howe, Angela Lamarca, Léamarie Meloche-Dumas, Frédéric Mercier, Sten Myrehaug, Julie Perinel, Charles De Ponthaud, Ville Sallinen, Yun Song, Heather Stuart, Eva T Janson, Pascale Tinguely, Francesca Tozzi, Tessa van Ginhoven, Susanne Warner, Kjetil Soreide, Stefano Partelli, Surgical management of small intestinal neuroendocrine tumours, BJS, Volume 113, Issue 3, March 2026, znag016, https://doi.org/10.1093/bjs/znag016

Includes:

1. Should the primary SI-NET be resected with unresectable stage IV disease?

2. When should peritoneal carcinomatosis from SI-NETs be resected?

3. When should liver metastases from SI-NETs be debulked?

4. When to consider liver transplantation for SI-NET liver metastases?

5. Intraoperative considerations—surgical techniques

6. How should intraoperative carcinoid crisis be managed?

7. When to give adjuvant therapy for completely resected SI-NETs?

Conclusion to this excellent paper

“Surgery for SI-NETs demands a fundamentally different mindset that balances oncological management with preservation of function, symptom control, and decades-long survivorship with active disease. This BJS Commission brought together international expertise to distil best current practice across the perioperative continuum, from meticulous preoperative work-up and mesentery-sparing techniques to evidence-based crisis management and the role of perioperative systemic therapy.

While much of current practice has been guided by tradition and single-centre experience, a shift is being witnessed. Advances in biomarkers, imaging, and systemic therapy provide a strong foundation on which to refine and expand surgical strategies. Key questions, such as those involving the optimal timing and extent of resection, selection for cytoreduction, the role of transplantation, and perioperative management, remain. Answering them will require sustained international collaboration, prospective multi-institutional data, and working hand in hand with other oncology specialists involved in the care of patients with NETs. There are unique opportunities for coordinated efforts to close the evidence gaps outlined herein, reduce variation in surgical care, and deliver the best possible outcomes for every patient with SI-NETs.”

Updated 25th August 2024 to add data on scenarios of liver and peritoneal metastases, plus a review of the Influence of Lymphatic, Microvascular and Perineural Invasion on Oncological Outcome in Patients with Neuroendocrine Tumors of the Small Intestine. It also incudes links to the European Neuroendocrine Tumor Society (ENETS) 2024 guidance paper for the management of well-differentiated small intestine neuroendocrine tumours

Small Intestine Neuroendocrine Tumours (SI NET) are one of the most common types of Neuroendocrine Cancer, and also one of the most challenging to diagnose and then treat. Patients can have a very good outlook even when presenting with metastatic disease. However, it’s true to say that some NET centres of excellence (CoE) or multi-disciplinary team (MDT) see a lot of SI NET patients have built up considerable experience in treating them, including the use of surgery. The surgical challenges are such that a surgeon not experienced in treating these cases may shy away or think they are inoperable, whereas MDTs or CoEs potentially have the experience available to operate or to make sound judgements based on their own experience. At the very least, they can offer a second opinion.

I wrote about my own experiences in “Small Intestine, Large Surgery” where I quoted one NET specialist who said “this is not normal bowel surgery”. I had a surgeon who believed in aggressive approaches in the first 12 months after diagnosis but would emphasise that not everyone can go down this route, patients much be carefully selected, there are many factors involved. There are some data available to show the benefits of upfront surgical resection for SI NETs and they can be found in the link above.

This is a huge subject within my group, bringing up many posts and comments from across the world. Some of the questions patients have span the spectrum of clinical situations in which questions frequently arise in the management of patients with SI NETs, where the answers are not clear from the literature. Many doctors and surgeons specialising in the care of NET patients generally agree on some of the approaches outlined below. I was delighted to see this document attached where a group of specialists reviewed the relevant data addressing many questions and have put forth consensus recommendations. Here’s a quote from the document to set the scene: “The objective of this conference was to improve the care of NET patients by increasing awareness of treatment options and providing expert recommendations based on clinical experience and careful review of the literature. Although the lack of randomized trials makes it difficult to prove the validity of these clinical recommendations, consensus or near consensus of our expert panel was reached for all of these questions. Our hope is that this article will offer guidance for physicians struggling to decide on how to deliver optimal care to their patients with SBNETs” (note: NANETS use SBNETs (Small Bowel NETs) rather than the use of “SI NETs” in ENETS guidelines).

Small intestine NET is one of the most common types and incidence is increasing fast including at earlier stages due to advances in imaging tech and screening activities; and more awareness in primary and secondary care. The statement below (made in 2017) is therefore interesting when you look at some of the big names in the list of contributors. The 2017 NANETS guidance on Small Intestine is worth a read while we await the latest version.

“this is not normal bowel surgery”

ENETS surgical guidelines emphasise the importance of “running the bowel”

“What Is the Best Procedure for Detecting Multifocal siNETs?” (1). Multifocal siNETs occur in around 20–30% of patients and their correlation with a poorer prognosis is controversial. CT and MR have demonstrated a very low accuracy in detecting multifocal siNETs. An accurate and systematic intraoperative bidigital palpation of the entire small intestine from the ligament of Treitz to the caecal valve bowel has been demonstrated to be more effective in detecting multifocal siNETs compared with all preoperative imaging modalities.”.

(1) – ENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumours: Surgery for Small Intestinal and Pancreatic Neuroendocrine Tumours. Neuroendocrinology, 25 Feb 2017, 105(3):255-265
DOI: 10.1159/000464292 PMID: 28237989 (Login required)

Click the blue link above to see the abstract or login if you have the credentials.

Click to read the latest ENETS Guidelines published in 2024. This is more of a guideline but does cover surgical approaches alongside other treatments

Multiple primary SI NET

This recent Swedish study confirms the importance of ‘running the bowel’ due to the potential for each small bowel primary NET to generate its own metastases. Read more by clicking here or on the graphic.

Influence of Lymphatic, Microvascular and Perineural Invasion on Oncological Outcome in Patients with Neuroendocrine Tumors of the Small Intestine – PMC (nih.gov)

Conclusion: Lymphatic, microvascular and perineural invasion were associated with worse recurrence-free and disease-free survival in patients with siNET. Therefore, these features should be considered when making decisions about adjuvant therapy and follow-up regimens. Authors cautioned that there were limitations to their study, e.g.

“Interestingly, there was no association between L, V and Pn invasion and the well-established predictive factor of tumor grading, suggesting an independent effect on disease recurrence and progression. In addition, we did not find any association between LI, VI and PnI and overall survival, which may not be totally surprising considering the overall good prognosis of siNET patients even in advanced and metastatic tumor stages.

Our study has some limitations. As per its retrospective nature, a selection bias cannot be excluded completely. Secondly, the limited size and the partly missing histopathologic data have to be mentioned and kept in mind when interpreting the results, especially with regards to perineural invasion. However, considering the rarity of the disease, this cohort with more than 160 included patients still represents a rather large study population. Due to the inclusion of patients from a relatively long study period, differences in the routine histopathologic assessment occurred, resulting in missing data when histologic parameters could not be retrieved from the medical records and the tumor specimens could not be re-evaluated anymore.”

Click the blue link to read the data.

Butz F, Dukaczewska A, Kunze CA, Krömer JM, Reinhard L, Jann H, Fehrenbach U, Müller-Debus CF, Skachko T, Pratschke J, Goretzki PE, Mogl MT, Dobrindt EM. Influence of Lymphatic, Microvascular and Perineural Invasion on Oncological Outcome in Patients with Neuroendocrine Tumors of the Small Intestine. Cancers (Basel). 2024 Jan 11;16(2):305. doi: 10.3390/cancers16020305. PMID: 38254794; PMCID: PMC10813650.

Value of Surgical Cytoreduction in Patients with Small Intestinal Neuroendocrine Tumors Metastatic to the Liver and Peritoneum | Annals of Surgical Oncology (springer.com)

Conclusion: Patients with siNETs metastatic to both the liver and peritoneum have favourable outcomes after aggressive surgical cytoreduction, with the best outcomes observed after complete cytoreduction. Therefore, the presence of peritoneal metastases should not by itself preclude surgical cytoreduction in this population.

Click the blue link to read the data.

Hallbera Gudmundsdottir MD, Alessandro Fogliati MD, Travis E. Grotz MD, Cornelius A. Thiels DO, Susanne G. Warner MD, Rory L. Smoot MD, Mark J. Truty MD, Michael L. Kendrick MD, David M. Nagorney MD, Thorvardur R. Halfdanarson MD, Sean P. Cleary MD & Patrick Starlinger MD

Value of Surgical Cytoreduction in Patients with Small Intestinal Neuroendocrine Tumors Metastatic to the Liver and Peritoneum. Ann Surg Oncol 31, 5370–5376 (2024). https://doi.org/10.1245/s10434-024-15316-7

Note: Some of you may have fibrosis in the ‘retroperitoneum’ (behind the peritoneum) but you can find info on that by clicking here.

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Thanks for reading.

Ronny