Metastatic well-differentiated pancreatic neuroendocrine tumors to the liver: a narrative review of systemic and surgical management

Pancreatic neuroendocrine tumors (PNETs) are a rare group of neoplasms originating from the endocrine pancreas. PNETs are classified as functional or non-functional tumors. PNETs are more often diagnosed at a higher stage with distant metastases or advanced locoregional disease. The majority of individuals with hepatic metastases will ultimately die of liver failure; therefore, the treatment of liver tumor burden is critical to providing a survival impact. While surgical resection remains the only chance of cure for disease confined to the pancreas or for locoregional disease, the treatment of advanced or metastatic PNETs is more complex and often requires a multimodal approach. This review focuses on treatment options for well and moderately differentiated PNETs with metastatic disease to the liver. These include surgery, liver-directed therapies including ablative and intra-arterial therapies, and systemic therapies such as somatostatin analogues, targeted therapies, chemotherapy, and peptide receptor radionuclide therapy. Developing an individualized treatment strategy requires careful assessment of liver tumor burden and predicted biological behavior. Aggressive surgical resection of hepatic metastases secondary to PNET primary tumors is associated with improved survival in multiple retrospective studies. General goals of treatment for metastatic disease include prolonging overall survival and progression free survival, improving quality of life, and control of symptoms.