Proton Beam Therapy for Unresectable Liver Metastasis

Inclusion Criteria: * pathologically diagnosed cancer patient * confirmed liver metastasis via computed tomography (CT) or magnetic resonance imaging (MRI) or biopsy * unresectable or unsuitable for RFA * solitary liver metastasis or less than 3 metastatic lesions if the distance is less than 3 cm between metastatic lesions * case discussed by surgeon, radiologist, and radiation oncologist * Eastern cooperative oncology group performance status 0 to 2 * optimal liver and renal function (Child-Pugh score 10 or less) * informed consent * agree to be contraceptive for the duration of the study and for the next 6 months Exclusion Criteria: * uncontrolled ascites or hepatorenal syndrome * status of pregnancy or breast-feeding * less than 12 weeks of expected survival * combined disease known to have high radiation side effects * serious acute illness that is not treated other than liver disease