Diagnostic Approach for Carcinoid Syndrome

Diagnostic Evaluation Algorithm

The National Comprehensive Cancer Network recommends multiphasic CT or MRI imaging of the abdomen and pelvis to localize the suspected neuroendocrine tumor, followed by somatostatin receptor scintigraphy (Octreoscan) for patients with suspected carcinoid syndrome 1, 2
Chromogranin A is the best general serum marker for neuroendocrine tumors, with elevated levels in 60% or more of patients with both functioning and non-functioning neuroendocrine tumors 2
Before proceeding with advanced imaging, it is essential to rule out false positives by confirming the patient is not taking proton pump inhibitors and does not have renal failure, liver failure, hypertension, or chronic gastritis 3, 2
Elevated chromogranin A levels twice the normal limit or higher correlate with tumor volume and are associated with shorter survival times (HR, 2.8; 95% CI, 1.9–4.0; P<.001) 2

A multiphasic CT/MRI scan of the abdomen and pelvis should be performed to localize the tumor and confirm the diagnosis, as recommended by the National Comprehensive Cancer Network 1
Somatostatin receptor scintigraphy (Octreoscan) should follow, as it can detect tumors that may be missed by other diagnostic studies 4

The National Comprehensive Cancer Network recommends measuring 24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of serotonin, particularly useful for serotonin-producing carcinoids 5, 2
Patients should avoid certain foods and substances that can increase 5-HIAA levels, such as avocados, bananas, and coffee, for 48 hours before collection 5

The American College of Chest Physicians recognizes the risk of carcinoid crisis, which can cause bronchospasm, hypotension, arrhythmias, and cardiopulmonary failure, and recommends prophylactic administration of octreotide acetate to prevent, abort, or treat carcinoid crisis 4
Rising chromogranin A levels in an asymptomatic patient with stable imaging does not necessarily indicate the need for new therapy, according to the National Comprehensive Cancer Network 5, 2