This is a Phase III trial comparing hepatic intra-arterial injection of Yttrium-90 microspheres (selective internal radiation [SIR] spheres) versus infusional intravenous (IV) 5FU in colorectal cancer metastatic to the liver only and refractory to standard IV chemotherapy.

Inclusion Criteria:

• Histologically proven colorectal adenocarcinoma, metastatic to the liver only.
• Failure of prior chemotherapy for advanced colorectal cancer.
• Adequate laboratory values of hematologic, renal and liver function
• World Health Organization (WHO) performance status (PS) <= 2
• Written consent

Exclusion Criteria:

• Pregnant or lactating patients
• Other tumor type than adenocarcinoma (leiomyosarcoma; lymphoma).
• Patients with cirrhosis or other chronic liver disease
• Thrombosis of the hepatic main artery of the portal vein
• Lung shunting > 20% as determined by nuclear medicine breakthrough scan
• Patients with serum bilirubin > 1.0 x upper limit of normal (ULN) or with AST and/or ALT and/or alkaline phosphatase > 5 x ULN
• Patients with concurrent or within 4 week period administration of any other experimental drugs.
• Other serious illness or medical conditions.