From the Guidelines
The recommended workup for suspected carcinoid syndrome begins with measuring 24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA) and serum chromogranin A levels, followed by imaging studies such as CT or MRI of the abdomen and pelvis, and somatostatin receptor scintigraphy (Octreoscan) or gallium-68 DOTATATE PET/CT scans. These biochemical markers are elevated in most patients with carcinoid syndrome and serve as the initial diagnostic tests 1. Additional blood tests should include complete blood count, comprehensive metabolic panel, and serum serotonin levels. Imaging studies are essential and should include a CT scan or MRI of the abdomen and pelvis to locate the primary tumor, which is commonly found in the small intestine, appendix, or lungs. For patients with suspected lung carcinoid, a chest CT is recommended 1.
Key Diagnostic Tests
- 24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA)
- Serum chromogranin A levels
- Complete blood count
- Comprehensive metabolic panel
- Serum serotonin levels
- CT or MRI of the abdomen and pelvis
- Somatostatin receptor scintigraphy (Octreoscan) or gallium-68 DOTATATE PET/CT scans
- Echocardiography to assess for carcinoid heart disease If a tumor is identified, tissue biopsy is necessary for definitive diagnosis, typically performed via endoscopy, bronchoscopy, or image-guided techniques depending on tumor location 1. This comprehensive approach allows for accurate diagnosis and staging, which are crucial for determining appropriate treatment strategies for carcinoid syndrome.
Additional Considerations
- Patients should be advised to avoid certain foods and medications that can affect 5-HIAA test results, such as avocados, bananas, and acetaminophen 1
- Surveillance of carcinoid tumors should include complete patient history and physical examination (H&P) and consideration of imaging studies, such as CT (abdominal and/or pelvic triple-phase) and MRI 1
From the Research
Diagnostic Approach
The diagnostic approach for suspected carcinoid syndrome involves several steps, including:
- Clinical evaluation: Patients with carcinoid syndrome often present with symptoms such as flushing, diarrhea, and wheezing 2, 3, 4, 5.
- Biochemical tests: Measurement of serum and urinary 5-hydroxyindoleacetic acid (5-HIAA) is a key diagnostic tool for carcinoid syndrome 2, 3, 4, 5, 6.
- Imaging studies: Various imaging techniques such as ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and somatostatin receptor scintigraphy (OCTREOSCAN) can be used to localize the primary tumor and detect metastases 2.
Biochemical Markers
Biochemical markers such as serum chromogranin-A (CgA) and urinary 5-HIAA are useful for diagnosing and monitoring carcinoid syndrome:
- Serum CgA is a sensitive marker for neuroendocrine tumors, including carcinoids 2.
- Urinary 5-HIAA is a specific marker for carcinoid syndrome, but its measurement can be prone to sampling errors 6.
- Serum 5-HIAA measurements may be a more reliable and convenient alternative to urinary 5-HIAA measurements for diagnosing carcinoid syndrome 6.
Imaging Techniques
Imaging techniques play a crucial role in localizing the primary tumor and detecting metastases:
- OCTREOSCAN is a sensitive imaging technique for detecting somatostatin receptor-positive tumors, including carcinoids 2, 3.
- Other imaging techniques such as CT, MRI, and ultrasound can also be used to localize the primary tumor and detect metastases 2.
Treatment Approach
The treatment approach for carcinoid syndrome depends on the extent of disease and symptoms:
- Somatostatin analogues such as octreotide are effective in controlling symptoms and stabilizing tumor growth in patients with carcinoid syndrome 2, 3, 4, 5.
- Interferon-alpha can be added to somatostatin analogues in patients who do not respond to octreotide alone 4, 5.
- Surgical resection of the primary tumor is the treatment of choice for non-metastatic tumors 2.