Liver-Directed Therapy for Neuroendocrine Metastases: From Interventional Radiology to Nuclear Medicine Procedures

SIMPLE SUMMARY: Approximately 80% of metastatic patients with gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) have secondary hepatic lesions, and in approximately 50% of cases, the liver is the only metastatic site. In patients with hepatic metastases from NENs for whom surgical treatment is contraindicated (high liver involvement, inaccessible localizations), percutaneous or intra-arterial treatments are safe and effective options to achieve disease control. In selected patients, liver-directed therapy could allow the improvement of clinical symptoms and biological abnormalities related to tumor secretion. However, toxicity and quality of life are also important elements in therapeutic decisions and must be considered for each single patient. Prospective studies are necessary to define the best treatment combination, including systemic and local options, to improve patient management. ABSTRACT: Neuroendocrine neoplasms (NENs) are rare and heterogeneous epithelial tumors most commonly arising from the gastroenteropancreatic (GEP) system. GEP-NENs account for approximately 60% of all NENs, and the small intestine and pancreas represent two most common sites of primary tumor development. Approximately 80% of metastatic patients have secondary liver lesions, and in approximately 50% of patients, the liver is the only metastatic site. The therapeutic strategy depends on the degree of hepatic metastatic invasion, ranging from liver surgery or percutaneous ablation to palliative treatments to reduce both tumor volume and secretion. In patients with grade 1 and 2 NENs, locoregional nonsurgical treatments of liver metastases mainly include percutaneous ablation and endovascular treatments, targeting few or multiple hepatic metastases, respectively. In the present work, we provide a narrative review of the current knowledge on liver-directed therapy for metastasis treatment, including both interventional radiology procedures and nuclear medicine options in NEN patients, taking into account the patient clinical context and both the strengths and limitations of each modality.