Regional therapies for the treatment of primary and metastatic hepatic tumors: A disease-based review of techniques and critical appraisal of current evidence

The practice of hepatic surgery has become increasingly complex as additional therapeutic options emerge to treat both primary and metastatic tumors of the liver. Liver-directed therapy options include selective internal radiation therapy (SIRT), stereotactic body radiation therapy, chemoembolization, bland embolization, hepatic artery infusion chemotherapy (HAIC), and ablative techniques such as microwave or radiofrequency ablation. Hepatocellular carcinoma has been treated with many of these therapies for palliation of symptoms, definitive treatment, and as a bridge to transplantation. Intrahepatic cholangiocarcinoma, particularly patients with unresectable disease, have demonstrated clinical responses to both SIRT as well as HAIC. Colorectal liver metastases have been treated with all of these techniques with varying degrees of success depending on the clinical scenario. A detailed understanding of these technologies and the evidence supporting their use is essential for the modern hepatic surgeon to properly sequence therapies and provide salvage options when first-line treatment has failed. This review describes these techniques and their appropriate usage based on the disease of interest and the respective evidence currently available.