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Small intestinal neuroendocrine tumours are slow-growing hormone-producing tumours of the ileum and jejunum, often found only after they have spread to lymph nodes and the liver. Monthly somatostatin analogue injections control symptoms and growth, lutetium-177 dotatate is the main second treatment, and everolimus, cabozantinib and surgery fill in.
Small intestinal neuroendocrine tumours arise from enterochromaffin cells of the distal jejunum and ileum, are often multiple along the same segment, and stay small while their mesenteric node metastases and the fibrosis around them grow large enough to kink the bowel and its blood supply. Most are well differentiated with a low Ki-67 index, nearly all express somatostatin receptor 2, and about a fifth to a third of patients with liver metastases develop carcinoid syndrome from serotonin that escapes the liver's first-pass clearance; years of exposure can scar the right-sided heart valves. Diagnosis rests on somatostatin receptor PET, chromogranin A and 24-hour urinary 5-HIAA, and the grade is read from Ki-67 and mitotic count on biopsy.
The treatment sequence was built by a short chain of trials. PROMID (Journal of Clinical Oncology 2009) randomised 85 patients with treatment-naive metastatic midgut tumours to octreotide LAR or placebo and lengthened time to progression from 6.0 to 14.3 months, the first proof that a somatostatin analogue slows growth as well as symptoms; CLARINET (New England Journal of Medicine 2014) did the same for lanreotide across enteropancreatic tumours, with the median progression-free survival not reached against 18.0 months on placebo. NETTER-1 (New England Journal of Medicine 2017) then randomised 231 patients with midgut tumours progressing on octreotide to lutetium-177 dotatate with octreotide or to high-dose octreotide; 65.2 percent against 10.8 percent were progression-free at 20 months, responses rose from 3 to 18 percent, and the final analysis gave median overall survival of 48.0 against 36.3 months, a difference that did not reach statistical significance because of crossover. Lutathera was approved in 2018, and NETTER-2 (Lancet 2024) moved it to first line for grade 2 and 3 tumours with a Ki-67 of 10 percent or more, lengthening progression-free survival from 8.5 to 22.8 months. Everolimus earned its gut indication in RADIANT-4 (Lancet 2016), where progression-free survival was 11.0 against 3.9 months in non-functional lung and gastrointestinal tumours, and cabozantinib was approved in 2025 after the extra-pancreatic cohort of CABINET (New England Journal of Medicine 2024) showed 8.4 against 3.9 months.
Surgery keeps its place even in metastatic disease: resection of the primary with its mesenteric nodes prevents obstruction and ischaemia, and liver metastases are debulked, ablated or embolised when the liver dominates. Carcinoid syndrome is treated by raising the somatostatin analogue dose, adding telotristat ethyl for diarrhoea that persists (TELESTAR, 2017), and giving octreotide by infusion around operations and embolisation to prevent carcinoid crisis. The order of radioligand therapy, everolimus and cabozantinib after somatostatin analogues has never been randomised; COMPETE (Lancet 2025) showed 177Lu-edotreotide beat everolimus on progression-free survival in grade 1 to 2 gastroenteropancreatic tumours, alpha-emitting radioligands are in phase 3 after lutetium failure, and the oral somatostatin agonist paltusotine and a subcutaneous octreotide depot are being tested for carcinoid syndrome.
The commonest neuroendocrine tumour of the gut in Western series and now the commonest cancer of the small intestine; most are grade 1 or 2 and many are found only after they have reached the mesenteric nodes or the liver.
Right-sided tumours behave differently from left-sided and rectal ones; the colon drains along its mesenteric vessels, the rectum into the mesorectum and pelvic side wall.
Same organ: Colon cancer (adenocarcinoma of the colon), Micropapillary adenocarcinoma of the colon and rectum, Adenoma-like adenocarcinoma of the colon and rectum, Lynch syndrome-associated colorectal cancer, Familial adenomatous polyposis-associated colorectal cancer, Mucinous adenocarcinoma of the colon and rectum, Signet ring cell carcinoma of the colon and rectum, Medullary carcinoma of the colon, Serrated adenocarcinoma of the colon and rectum, Peritoneal mesothelioma, Colorectal cancer, Rectal cancer, Mismatch-repair deficient (MSI-high) colorectal cancer, BRAF V600E-mutant colorectal cancer, HER2-amplified colorectal cancer, KRAS G12C-mutant colorectal cancer, Early-onset colorectal cancer (under 50), Anal cancer (squamous cell carcinoma), Appendiceal cancer and pseudomyxoma peritonei, Small intestine cancer (small bowel adenocarcinoma), Anal high-grade squamous intraepithelial lesions (precursor), Localised anal squamous cell carcinoma (stage I to III), Metastatic and recurrent anal squamous cell carcinoma, Low-grade appendiceal mucinous neoplasm and pseudomyxoma peritonei, Appendiceal adenocarcinoma (mucinous and non-mucinous, including signet ring cell), Goblet cell adenocarcinoma of the appendix, Localised small bowel adenocarcinoma (stage I to III, resected), Advanced and metastatic small bowel adenocarcinoma
Biopsy with Ki-67 grading, somatostatin receptor PET, cross-sectional imaging of the liver, chromogranin A and urinary 5-HIAA, echocardiography if carcinoid syndrome is present.
Segmental small bowel resection with mesenteric lymphadenectomy, inspecting the whole small bowel for further primaries; the primary is often removed even when liver metastases are present.
Octreotide LAR or lanreotide (PROMID, CLARINET); lutetium-177 dotatate first line for grade 2 to 3 tumours with a Ki-67 of 10 percent or more (NETTER-2).
Lutetium-177 dotatate (NETTER-1); everolimus (RADIANT-4); cabozantinib (CABINET); liver-directed therapy for hepatic-dominant disease.
Somatostatin analogue dose escalation, telotristat ethyl for refractory diarrhoea, octreotide infusion around procedures to prevent carcinoid crisis, valve surgery for carcinoid heart disease.
Everolimus or cabozantinib; 177Lu-edotreotide if approved; alpha-emitting radioligands and retreatment in trials.
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Cabozantinib is approved for previously treated neuroendocrine tumours of any origin and is a standard later-line choice, including for lung carcinoids.
Patients newly diagnosed with an advanced grade 2 or 3 neuroendocrine tumour of the gut or pancreas that shows somatostatin receptors on imaging can now receive lutetium dotatate as their first treatment, gaining more than a year of additional disease control and a much higher chance of tumour shrinkage. It does not settle whether radioligand therapy is better than other first-line options such as capecitabine-temozolomide or everolimus, and long-term marrow safety with earlier use needs surveillance.
Lutetium-177 dotatate is a standard treatment for progressive small bowel neuroendocrine tumours after somatostatin analogues, and NETTER-2 has since moved it into first-line use for higher-grade tumours.
Everolimus is approved for progressive lung and gastrointestinal neuroendocrine tumours and is a standard option after somatostatin analogues, particularly in lung carcinoids where radioligand therapy is off label.
Somatostatin analogues are the standard first-line antiproliferative treatment for grade 1 to 2 gastroenteropancreatic neuroendocrine tumours whether or not they cause a hormone syndrome.
Octreotide LAR became a standard first-line antiproliferative therapy for small intestinal neuroendocrine tumours, later joined by lanreotide after CLARINET.
Query for this cancer: (TITLE:"Small intestinal neuroendocrine tumours" OR ABSTRACT:"Small intestinal neuroendocrine tumours" OR TITLE:"Midgut neuroendocrine tumour" OR ABSTRACT:"Midgut neuroendocrine tumour" OR TITLE:"Small bowel NET" OR ABSTRACT:"Small bowel NET" OR TITLE:"Ileal carcinoid" OR ABSTRACT:"Ileal carcinoid" OR TITLE:"Jejunoileal neuroendocrine tumour" OR ABSTRACT:"Jejunoileal neuroendocrine tumour" OR TITLE:"SI-NET" OR ABSTRACT:"SI-NET") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Small intestinal neuroendocrine tumours, not a curated reading list.
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Sudden severe bone pain, or back pain with weakness or numbness in the legs (possible spinal cord compression).
Sudden severe abdominal pain, a hard or very tender abdomen, or abdominal pain with vomiting and fever. Boxed warning for gastrointestinal perforation on bevacizumab.
Fainting, near-fainting, or an irregular or racing heartbeat; several kinase inhibitors prolong the QT interval and the labels require ECG and electrolyte monitoring.
Tablets: take on an empty stomach (no food 2 hours before or 1 hour after). Avoid grapefruit.
Avoid grapefruit. Live vaccines are contraindicated.
Reduce to 40 mg daily in moderate impairment; avoid in severe.
See all on the product pages:177Lu-edotreotide212Pb-DOTAMTATEActinium-225 DOTATATECabozantinibEverolimusLutetium-177 dotatate·Printable cards in the navigator
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