Carcinoid syndrome

Disease Description (Causes and Symptoms)

• Definition and cause: A syndrome caused by carcinoid tumors (neuroendocrine tumors) originating from neuroendocrine cells in the intestines, bronchi, and other sites, which excessively secrete various vasoactive substances such as serotonin, histamine, and calcitonin-like peptides. Primary tumors mainly occur in the small intestine, large intestine, and appendix, and the secreted substances often cause systemic symptoms only when liver metastasis is present.
• Pathophysiology: When substances secreted by the tumor, particularly serotonin, are not metabolized in the liver and enter the systemic circulation, they can cause vasodilation, increased intestinal motility, bronchoconstriction, and fibrosis of the heart valves.
• Main symptoms
  • Flushing of the face and upper body: Occurs in approximately 70% of patients and is triggered by stress, alcohol, exercise, cheese, and other factors
  • Diarrhea and abdominal pain: Increased intestinal motility caused by serotonin
  • Bronchoconstriction (asthma-like symptoms): Occurs episodically in approximately 15–20% of patients
  • Carcinoid heart disease (valvular abnormalities, particularly tricuspid regurgitation): Frequently accompanies the syndrome (observed at high rates depending on the report)
  • Other symptoms: Fever, weight loss and malnutrition, features of acromegaly, decreased libido and erectile dysfunction, skin lesions, cyanosis, and others

Treatment Methods

• Curative treatment
  • Surgical resection: Complete resection of the primary tumor and metastatic lesions when possible is the top priority.
  • If liver metastasis is present and complete resection is possible, curative liver resection may be considered.
• Symptom control and systemic treatment
  • Somatostatin analogs (SSAs): Octreotide and lanreotide — first-line drugs for suppressing secretion and relieving symptoms. They also have an effect on inhibiting tumor growth.
  • Telotristat (tryptophan hydroxylase inhibitor): Used for diarrhea that is resistant to SSAs.
  • PRRT (such as 177Lu-DOTATATE): Effective for symptom control and inhibiting tumor growth in somatostatin receptor-positive tumors.
  • Locoregional liver treatment: Liver resection, embolization (hepatic artery embolization or chemoembolization), hepatic artery infusion therapy, and others.
  • Targeted therapy, immunotherapy, and chemotherapy: For advanced disease or specific pathological types, everolimus and cytostatic chemotherapy (for example, streptozocin-based regimens or regimens including temozolomide) may be considered.
• Carcinoid crisis (acute worsening of symptoms during surgery or manipulation)
  • Prophylactic and therapeutic high-dose intravenous octreotide (combined with fluid and hemodynamic support and, if necessary, vasopressors).
• Cardiac treatment
  • If carcinoid heart disease progresses and affects cardiac function, cardiac surgery such as valve replacement may be considered (in consultation with cardiology and cardiothoracic surgery).
• Lifestyle management and nutrition
  • Avoid triggers (alcohol, certain foods such as cheese and fermented foods, and stress), manage dehydration and electrolytes caused by diarrhea, and provide nutritional supplementation and testing/supplementation for niacin deficiency when necessary.
• Precautions
  • Establish a plan to prepare and administer octreotide to prevent carcinoid crisis before surgery or procedures.
  • Regular echocardiography (to monitor valvular changes), biochemical markers (urine 5-HIAA and blood chromogranin A), and imaging follow-up are recommended.

Checklist Before an Outpatient Visit (Including Examples of Items to Bring and Questions)

• Items to bring
  • List of medications currently being taken (including prescriptions, OTC medicines, and supplements)
  • Copies of previous pathology tests (tumor biopsy), surgical records, and recent imaging (CT/MRI and PET)
  • Recent test results (blood tests, urine 5-HIAA results, and others)
  • Symptom diary: Frequency, duration, triggers, and severity of flushing, diarrhea, and shortness of breath
  • Allergy history and whether there is a history of heart disease
• Information that is helpful to provide to the medical staff during the outpatient visit
  • When the symptoms first began and how they have progressed
  • Changes in weight, fever, and whether nighttime symptoms are present
  • For women, the possibility of pregnancy or whether they are breastfeeding

Examples of General Questions to Ask the Doctor

• What is my stage of this disease (is there metastasis)? What additional evaluations are needed through imaging and tests?
• Which medications can best control my current symptoms (flushing and diarrhea), and what side effects can be expected?
• What are the indications and expected benefits of surgery or procedures (such as liver resection and PRRT)?
• How high is my risk of developing carcinoid heart disease, and how will it be monitored?

Examples of Disease-Specific Questions

• In my case, based on the test and imaging findings, is treatment with a somatostatin analog recommended? How will the treatment response be evaluated?
• What is the specific plan to prevent carcinoid crisis before and after surgery (primary tumor or liver resection), including the octreotide dose and infusion method?

Additional information: If needed, sharing recent test results (biopsy, urine 5-HIAA, somatostatin receptor imaging, and others) will allow more specific diagnostic and treatment recommendations and pre-visit preparations to be organized.