Selective internal radiation therapy (SIRT): a new modality for treating patients with colorectal liver metastases.

BACKGROUND: Selective internal radiation therapy (SIRT) is a new and developing modality for treating non-resectable liver tumours. Evidence is emerging that it is very efficacious in patients with hepatocellular cancer and colorectal liver metastases. DISCUSSION: SIRT generally involves a single delivery of (90)yttrium micro-spheres into the hepatic artery. Preferential uptake is achieved into liver tumours, because of their predominant hepatic arterial blood supply. Average tumour doses of radiation in excess of 200 Gy are achieved. The treatment is generally well tolerated and has been documented by a number of groups internationally to achieve response rates of around 90% in patients with extensive colorectal cancer (CRC) liver metastases. Since the product obtained FDA approval in the USA in 2002, it is being more widely employed and investigated. Unlike other ablative therapies being applied to non-resectable liver tumours, SIRT is indicated even in patients with an extensive burden of liver tumour. Indications, dosing schedules and expected outcomes will become better defined as more groups take up the treatment.