Neuroendocrine tumor

Neuroendocrine neoplasms arise in different organs, commonly the digestive tract, pancreas and lungs. This guide focuses on well-differentiated neuroendocrine tumors (NETs). Poorly differentiated neuroendocrine carcinoma (NEC), including small-cell and large-cell forms, is a different category. A diagnosis of grade 3 alone does not establish NEC.

For digestive NETs, grading uses Ki-67 and mitotic activity: the Ki-67 bands are below 3% for G1, 3–20% for G2 and above 20% for G3, interpreted with the mitotic count and morphology. When measures disagree, the higher proliferative grade matters. Lung carcinoids use site-specific criteria centered on mitoses and necrosis; the digestive Ki-67 scheme should not simply be copied across.

Grade is not stage. A low-grade tumor can metastasize, while a higher-grade lesion may still be localized. If an old, small biopsy no longer explains rapidly changing disease, expert review or repeat sampling of a progressing site can clarify whether the biology has changed.

If the pathology says poorly differentiated NEC, use the dedicated guide to frame the treatment discussion.

Some NETs are nonfunctioning: they do not cause a recognizable hormone syndrome, yet can still grow or spread. Others produce hormones that cause problems disproportionate to tumor size. Pancreatic examples include insulin-related low blood sugar or gastrin-related acid disease. Flushing and secretory diarrhea can occur with carcinoid syndrome, but these symptoms have many other causes.

Testing should follow the clinical syndrome rather than ordering every hormone indiscriminately. Chromogranin A alone neither proves NET nor reliably establishes progression; medicines such as proton-pump inhibitors and other conditions can affect results. Depending on the situation, the team may use specific hormone tests, serotonin-related markers, and cardiac assessment.

Contrast CT or MRI maps anatomy and disease extent; liver MRI may clarify small liver lesions. Somatostatin receptor (SSTR) PET, using an appropriate receptor-targeted tracer, identifies receptor-expressing disease and helps assess PRRT suitability. It complements rather than replaces anatomical imaging and pathology.

FDG PET can add information when disease is higher grade, growing quickly or inconsistent with the receptor scan. A receptor-positive lesion alongside a rapidly growing receptor-negative lesion raises a different treatment problem from uniformly receptor-positive disease. The team may need a biopsy of the discordant site before choosing one treatment for everything.

Surgery can provide long-term control and potential cure when disease is localized and completely resectable. The operation differs for a small rectal NET, a small-bowel primary with mesenteric involvement, a pancreatic NET or a lung carcinoid. Selected superficial digestive lesions may be removed endoscopically; others require formal surgery and nodal assessment.

Some small, asymptomatic nonfunctioning pancreatic NETs can be observed after specialist review. Size alone is insufficient: growth, grade, duct changes, location, inherited syndromes and surgical consequences matter. Surveillance is an active plan with imaging and criteria for intervention. Routine postoperative drug treatment has no established benefit after complete resection of a well-differentiated pancreatic NET.

Long-acting somatostatin analogues such as lanreotide or octreotide can control hormone symptoms and help slow growth in appropriate well-differentiated NETs. CLARINET established antiproliferative benefit for lanreotide in its studied enteropancreatic population. These drugs often stabilize disease rather than produce major shrinkage, so a rapidly threatening mass may require another strategy.

Persistent diarrhea despite treatment should prompt assessment for other causes as well as uncontrolled carcinoid syndrome. Telotristat may help selected patients with refractory carcinoid-syndrome diarrhea alongside a somatostatin analogue. Carcinoid heart disease needs dedicated surveillance and management. Before surgery, anesthesia or an invasive procedure, tell the team about hormone symptoms so a crisis-management plan can be prepared.

Peptide receptor radionuclide therapy (PRRT) delivers radiation through a receptor-binding medicine. Lutetium-177 dotatate has a US indication for SSTR-positive gastroenteropancreatic NETs in adults and children aged 12 or older. That indication should not be read as automatic approval for every lung NET or every high-grade neuroendocrine cancer.

Assessment includes receptor uptake across relevant lesions, blood counts, kidney and liver function, prior treatment and ability to follow radiation precautions. Treatment includes kidney-protective amino-acid infusion and coordinated somatostatin-analogue timing. Marrow suppression, kidney injury and uncommon delayed blood disorders are among the risks; functional tumors can also require precautions against hormonal crises.

NETTER-2 supports discussing lutetium-177 dotatate earlier for newly diagnosed, advanced, receptor-positive digestive NETs with a higher proliferation rate: the trial included Ki-67 from 10% to 55%. Progression-free survival improved compared with high-dose octreotide. It did not compare PRRT with CAPTEM or every other active treatment, and its results should not be applied to all G1 tumors or poorly differentiated NEC.

The 2026 COMPETE trial studied a different radiopharmaceutical, lutetium-177 edotreotide (ITM-11), against everolimus in progressive G1–G2 gastroenteropancreatic NETs and showed a progression-free survival benefit. This is not the same product as dotatate. In August 2026, the developer reported an FDA complete response letter concerning manufacturing and inspection issues; a positive trial did not mean the medicine was approved or routinely available.

Everolimus is an option for selected advanced NETs, including pancreatic and nonfunctioning gastrointestinal or lung disease; sunitinib has an established role in pancreatic NETs. These are not interchangeable approvals for every neuroendocrine tumor. Treatment choice accounts for growth rate, hormone syndrome, the need for shrinkage, diabetes, blood pressure and other health conditions.

In March 2025, the FDA approved cabozantinib for previously treated, unresectable locally advanced or metastatic well-differentiated pancreatic and extrapancreatic NETs in adults and children aged 12 or older. CABINET demonstrated longer progression-free survival in both groups. The approval does not establish cabozantinib as the first treatment for every NET; hypertension, diarrhea, fatigue and other toxicities can require monitoring and dose adjustment.

Chemotherapy is particularly relevant to pancreatic NETs when meaningful shrinkage or faster disease control is needed. In the randomized phase 2 E2211 trial, capecitabine plus temozolomide (CAPTEM) improved progression-free survival compared with temozolomide alone in the studied pancreatic NET population; an overall-survival advantage was not demonstrated. This evidence does not make CAPTEM the default for every intestinal or lung NET.

For well-differentiated G3 NET, treatment may include selected chemotherapy regimens, PRRT or other options according to primary site, Ki-67, receptor expression and tempo. Automatically treating it like poorly differentiated NEC can miss important differences. Conversely, a rapidly progressing receptor-negative tumor should not wait for a receptor-targeted strategy that is unlikely to cover its disease.

Selected patients with liver-dominant disease may benefit from surgery, ablation or an arterial liver-directed procedure, especially when hormone symptoms or a limited threatening tumor burden are the main problem. Decisions depend on distribution, liver reserve, extrahepatic disease, prior treatment and whether meaningful control is achievable. Liver involvement alone does not identify one best procedure.

Local procedures and systemic treatment should be planned together, including their effects on future PRRT and liver function. Small-bowel NETs can also cause obstruction or mesenteric fibrosis despite relatively slow tumor growth. Persistent abdominal pain, vomiting or an abrupt change in bowel symptoms needs assessment rather than waiting for the next routine scan.

Follow-up is tailored to site, grade, resection status, tumor burden, symptoms and treatment. Imaging assesses disease while blood tests and symptom review assess treatment effects and hormone activity. Some NETs recur late, so a reassuring early scan does not automatically end follow-up. Nutrition, pancreatic enzyme deficiency, glucose changes and heart problems may need active management.

Bring the full pathology with differentiation, Ki-67 and mitotic count; operation and endoscopy reports; original CT/MRI and receptor/FDG PET images when performed; hormone results; and a timeline of medicines, responses and adverse effects. Useful questions are: which lesion is driving the decision, do all important lesions express receptors, is the immediate goal symptom control or shrinkage, and what will remain available after this treatment?