Stereotactic Body Radiation Therapy (SBRT) for Unresectable Liver Metastases

Inclusion Criteria: * Karnofsky Performance Scale (KPS) equal or greater than 70 * 1 to 4 liver metastases with an individual maximum diameter of up to 5 cm * Lesions considered unresectable or patients considered unfit for surgery * Histology of the primary tumor: colorectal adenocarcinoma, carcinoma of the anal canal or gastrointestinal neuroendocrine tumors. * Absence of evidence of extra-hepatic disease or extra-hepatic disease to be treated with curative intent. * Minimum interval of 2 weeks between systemic chemotherapy and SBRT. * Adequate bone marrow function defined as: * absolute neutrophils count \> 1,800 cells / mm 3 * platelets \> 100,000 cells / mm 3 * hemoglobin \> 8.0 g / dl ( transfusion or other intervention accepted) Exclusion Criteria: * Concomitant chemotherapy * Prior radiotherapy to the upper abdomen * Pregnancy * Underlying Cirrhosis * Active hepatitis or clinically significant liver failure * Prior invasive neoplasm except for non-melanoma skin cancer, or unless more than five years without evidence of disease * Severe Comorbidity * Current anticoagulant treatment