Management of Vasovagal Episodes and Flushing Associated with Neuroendocrine Tumor Treatment

Understanding Neuroendocrine Tumors and Associated Symptoms

Neuroendocrine tumors (NETs) may secrete various hormones and vasoactive peptides that can cause symptoms including intermittent flushing and diarrhea (carcinoid syndrome) 3, 4
Approximately 8-28% of patients with NETs experience carcinoid syndrome, which typically occurs when liver metastases or retroperitoneal disease allow hormonal metabolites to enter systemic circulation 5

The National Comprehensive Cancer Network recommends somatostatin analogues as the first-line treatment for managing vasovagal episodes and flushing associated with neuroendocrine tumor treatment, with octreotide and lanreotide providing substantial relief of symptoms in the majority of patients 1, 2
Initial dosing of octreotide is 50-100 μg subcutaneously two or three times daily, can be titrated up to maximum daily dose of 1500 μg 1
Long-acting release (LAR) formulation of octreotide is 20-30 mg intramuscularly every 4 weeks 2
Short-acting octreotide can be added to LAR for rapid relief or breakthrough symptoms 2
Lanreotide has a similar mechanism of action as octreotide but is administered as a deep subcutaneous injection 2
The ELECT trial demonstrated significant reduction in rescue octreotide use compared to placebo (34% vs 49%, p=0.02) 2

Somatostatin analogues provide substantial relief of flushing and diarrhea in the majority of patients, though hormone levels may not normalize completely 1
Somatostatin analogues may help prevent advancement of carcinoid heart disease and intestinal fibrosis, although studies are conflicting 1
For patients undergoing procedures (surgery, anesthesia, hepatic artery embolization), increase coverage with short-acting octreotide by intravenous administration (50 μg/h) 6
Administer 12 hours before, during, and 48 hours after the procedure to prevent carcinoid crisis 1
For major procedures, preoperative IV bolus of 100-200 μg followed by continuous infusion of 50 μg/h is recommended 7

Monitor for potential side effects of somatostatin analogues: fat malabsorption, gallstones, vitamin A and D malabsorption, headaches, diarrhea, dizziness, and blood glucose fluctuations 1
Consider cardiology consultation and echocardiogram to assess for carcinoid heart disease, especially in patients with signs and symptoms of heart disease 2
Consider cardiology consultation and echocardiogram to assess for carcinoid heart disease, especially in patients planning major surgery 2
Consider cardiology consultation and echocardiogram to assess for carcinoid heart disease, especially in patients with 5-HIAA levels ≥300 mcmol (57 mg) over 24 hours 2
Consider cardiology consultation and echocardiogram to assess for carcinoid heart disease, especially in patients with three or more flushing episodes per day 2

Ondansetron can be useful for general symptom control in carcinoid syndrome 6
Cyproheptadine is occasionally used for carcinoid syndrome 6
For diarrhea control, pancreatic enzyme supplements can be used, noting that pancreatic insufficiency can occur with octreotide/lanreotide therapy 6
For diarrhea control, cholestyramine can be used 6