Approximately 20% of pancreatic neuroendocrine tumors (NETs) are hormonally functional, meaning that the tumor produces a measurable hormone that results in a clinical syndrome, states Jonathan R. Strosberg, MD. Examples include: VIPoma, producing watery diarrhea; insulinoma, resulting in hypoglycemia; and glucagonoma, causing diabetes, weight loss, and unusual skin rash.
Somatostatin analogs, such as octreotide and lanreotide, are the cornerstone of treatment for patients with metastatic disease with hormonal syndromes. These agents are particularly effective at managing VIPomas and glucagonomas, says James C. Yao, MD. Gastrinomas are often well controlled with proton pump inhibitors (PPIs), but somatostatin analogs may be administered in patients who are refractory to PPIs or have additional symptoms.
Using somatostatin analogs to treat insulin hypersecretion from insulinomas may cause down regulation of counter regulatory hormones, potentially exacerbating the hypoglycemia. Somatostatin analogs should be used cautiously in these cases, comments Yao.
Determining when to initiate systemic therapy often depends upon patient preference and disease state, says Yao. Patients with evidence of disease progression are typically started on systemic therapy, while individuals who remain asymptomatic with low volume disease may receive observational treatment. Yao’s typically initiates treatment relatively early in patients with heavy tumor burden or symptoms.
Results from the CLARINET study demonstrated the efficacy of lanreotide in a broad range of NETs, states Matthew H. Kulke, MD. These findings demonstrated that somatostatin analogs could effectively control symptoms as well as tumor growth. Octreotide is generally given as an intramuscular injection, while lanreotide is given as a deep subcutaneous injection, he adds.