Radiation therapy for primary and metastatic tumors of the liver

Abstract

Hepatic tumors can be either primary disease (i.e., hepatocellular carcinoma) or a site of metastases from other solid malignancies. The primary therapy for all liver tumors is resection, but only a minority of patients present with resectable disease. Various nonsurgical ablative techniques have been investigated to cure or palliate unresectable hepatic tumors by improving locoregional control. The objective of this article is to review the radiotherapy options in managing primary or metastatic liver cancer. Two emerging radical radiotherapy options include stereotactic body radiation therapy (SBRT) and selective internal radiotherapy (SIRT). SBRT delivers ablative doses of radiation in a hypofractionated course and has been used in metastatic disease to the brain, spine, lung, and liver. The local tumor control for SBRT appears to exceed that of conventional fractionation external beam radiotherapy (EBRT). SIRT, also known as radioembolization, is the intraarterial delivery of microspheres impregnated with yttrium-90 (Y90) via the hepatic artery. The evidence is limited to cohort and comparative studies with historical controls; nonetheless, results appear to be promising. Both SBRT and SIRT to liver tumors may serve as a bridge to liver transplantation (LT) and as a treatment strategy for metastasis from colorectal cancer to achieve the effect of metastasectomy. Meanwhile, combining molecular-targeted agents with radiotherapy is an emerging strategy to enhance the therapeutic ratio. SBRT and/or SIRT are promising local ablative modalities for management of unresectable liver tumors. Further well-designed trials are warranted to establish the proper combination of different therapeutic modalities.