Treatment options for unresectable neuroendocrine liver metastases

Hepatic metastases develop in 85% of patients with gastroenteropancreatic neuroendocrine tumors. Radical surgery, which involves resection of the primary and liver metastases, is the mainstay of treatment, with 60-70% 5-year survival and 35% 10-year survival rates. However, less than 15% of neuroendocrine tumor liver metastases (NETLMs) are resectable, owing either to multifocality or the inability to preserve sufficient parenchyma following resection. This article deals with the therapeutic modalities available for nonresectable liver metastases, and the therapeutic options available for management of nonresectable NETLMs are discussed. Targeted therapies for NETLMs include hepatic artery embolization, transcatheter arterial chemoembolization, radiolabeled/drug-eluting microspheres, radiofrequency ablation, cryoablation and phenol injection. Hepatic artery embolization/transcatheter arterial chemoembolization is associated with 75-100% symptom relief and an objective tumor response varying from 33 to 80%. Other modalities, such as biotherapy, peptide receptor therapy and chemotherapy, target both the primary and metastatic disease. Their effects on NETLMs as a subgroup have not been evaluated. Various therapeutic options are available for the treatment of unresectable NETLMs. Most offer significant symptomatic relief, with only a few comparative studies showing survival benefit. Most of the available evidence is based on retrospective and prospective case series rather than randomized controlled trials. Well-designed studies on existing treatment modalities and the search for newer therapeutic options are required.