Treatments for Hepatic and Neuroendocrine Tumors
The use of external-beam radiotherapy and the application of more advanced radiotherapy approaches (e.g., intensity-modulated radiotherapy) may be of limited use in individuals with multiple diffuse lesions due to the low tolerance of the normal liver to radiation compared with the higher doses of radiation needed to kill the tumor.
Radioembolization (referred to as selective internal radiotherapy in older literature) delivers small beads (microspheres) impregnated with yttrium-90 (Y90) intra-arterially via the hepatic artery. The microspheres, which become permanently embedded, are delivered to tumors preferentially because the hepatic circulation is uniquely organized, whereby tumors greater than 0.5 cm rely on the hepatic artery for blood supply while the normal liver is primarily perfused via the portal vein. Y90 is a pure beta-emitter with a relatively limited effective range and a short half-life that helps focus the radiation and minimize its spread.
In general, radioembolizationis used for unresectable hepatocellular carcinoma that is greater than 3 cm.
There is little information on the safety or efficacy of repeated radioembolization treatments or on the number of treatments that shouldbe administered.
Radioembolization shouldbe reserved for patients with adequate functional status (Eastern Cooperative Oncology Group Performance Status 0-2), adequate liver function and reserve, Child-Pugh class A or B, and liver-dominant metastases.
Symptomatic disease from metastatic neuroendocrine tumors refers to symptoms related to excess hormone production.
Practice Guidelines and Position Statements
National Comprehensive Cancer Network
Primary Hepatobiliary Carcinoma
The NCCN guidelines (v.1.2019) on the treatment of hepatobiliary carcinoma indicate that the use of arterially directed therapies, including transarterial bland embolization, transarterial chemoembolization, and drug-eluting beads transarterial chemoembolization, and RE with yttrium-90 microspheres may be appropriate provided that the arterial blood supply can be isolated without excessive nontarget treatment.
Metastatic Neuroendocrine Tumors
The NCCN guidelines (v.2.2019) on the treatment of neuroendocrine tumors give a category 2B recommendation for hepatic regional therapy (arterial embolization, chemoembolization, RE) in the setting of advanced locoregional disease.
Metastatic Colon Cancer
The NCCN guidelines (v.2.2019) on the treatment of colon cancer provides a consensus recommendation that: "…arterial-directed catheter therapy, in particular yttrium-90 microsphere selective internal radiation, is an option in highly selected individuals with chemotherapy-resistant/-refractory disease and with predominant hepatic metastases."