Liver transplantation in patients with liver metastases from neuroendocrine tumors: A systematic review

Background: Liver transplantation to treat neuroendocrine tumors, especially in the setting of diffuse liver involvement not amenable to operative resection remains controversial. We sought to perform a systematic review of the current literature to summarize data on patients undergoing liver transplantation with neuroendocrine tumors liver metastases as the indication.

Methods: A systematic review was conducted in accordance to the Preferred Reporting Items for Systematic reviews and Meta-Analysis guidelines. Eligible studies were identified using 3 distinct databases through March 2017: Medline (PubMed), ClinicalTrials.gov, and Cochrane library, Cochrane Central Register of Controlled Trials using a search algorithm: "(neuroendocrine or NET) and transplantation and liver."

Results: From the 1,216 records retrieved, 64 studies were eligible. Overall, 4 studies presented data from registries, namely the European Liver Transplant Registry and the United Network for Organ Transplantation/Organ Procurement and Transplantation Network databases, 3 were multicenter studies. The largest cohort of data on patients undergoing liver transplantation for neuroendocrine tumors liver metastasis indication were from single center studies comprising a total of 279 patients. Pancreas was the primary tumor site for most patients followed by the ileum. Several studies reported that more than half of patients presented with synchronous disease (55.9% and 57.7%); in contrast, metachronous neuroendocrine tumors liver metastasis ranged from 17.7% to 38.7%. Overall, recurrence after liver transplantation ranged from 31.3% to 56.8%. Reported 1-, 3-, and 5-year overall survival was 89%, 69%, and 63%, respectively. Several prognostic factors associated with worse long-term survival including transplantation >50% liver tumor involvement, high Ki67, as well as a pancreatic neuroendocrine tumors versus gastrointestinal neuroendocrine tumors tumor location.

Conclusion: Liver transplantation may provide a survival benefit among patients with diffuse neuroendocrine tumors metastases to the liver. However, due to high recurrence rates, strict selection of patients is critical. Due to the scarcity of available grafts and the lack of level 1 evidence, the recommendations to endorse liver transplantation for extensive liver neuroendocrine tumors metastases warrants ongoing deliberations.