Partial Liver Radiotherapy for Unresectable Liver Metastases

Inclusion Criteria: * liver metastases unequivocally seen on contrast enhanced CT and/or MRI from colon or rectal cancer, previously confirmed pathologically as adenocarcinoma * either 1) the tumor must be unresectable, 2) the patient must be medically inoperable, or 3) extra-hepatic metastases are present (making hepatic surgery an inappropriate treatment option) * good performance status (0-1) * Age \> 18 years. Adult patients of all ages, both sexes and all races will be included in this study. Female patients within reproductive years may not be, nor become, pregnant during participation in this study * life expectancy \> 3 months Exclusion Criteria: * patients with active hepatitis or clinically significant liver failure * patients receiving anticoagulation treatment with warfarin or heparin * prior radiation therapy to the right upper abdomen, precluding re-irradiation of the liver * clinically apparent ascites * central nervous system metastases