A Trial on SBRT Versus MWA for Inoperable Colorectal Liver Metastases (CLM)

Inclusion Criteria: * Age \>18 years * Karnofsky index \>70% * Histological proven adenocarcinoma of the colon or rectum with radiological (by CT- or MRI) or histological-/cytological verified liver metastases. * Metastases must be visible on diagnostic- and dose planning CT scans and on ultrasonography. * The patient should not be suitable for surgical resection due to technical or patient-related conditions. Resectability must be judged by a trained hepatobiliary surgeon and discussed in a multidisciplinary team meeting. * Presence of 1-3 lesions . * Diameter ≤ 40 mm. * All tumors should be feasible for treatment with each of the two modalities, SBRT and MWA * Adequate liver function: bilirubin \<1.5 mg/dl, alb\> 3.5g/dl, normal PT/PTT except if the patient uses anticoagulants, liver enzymes\<3 times upper limit of normal. No ascites. * Renal function must be adequate for infusion of iv. contrast for CT-scan. * Adequate bone marrow function: Hbg³8 g/dl, platelets³100.000 and leucocytes ³2.000/ml. * Informed consent. * Extrahepatic disease stable or in response after CT * No previous abdominal radiation therapy (RT) Exclusion Criteria: * Uncontrolled primary tumor or extrahepatic disease * Previous abdominal radiation therapy (RT) or other local conservative treatment on lesion target. * Pregnant or breastfeeding patients. * Prior malignancy within the last five years (except adequately treated basal cell carcinoma of the skin or in situ carcinoma of the skin or in situ carcinoma of the cervix, surgically cured, or localized prostate cancer without evidence of biochemical progression). * Previous inclusion in this study. * Underlying liver cirrhosis (Child-Pugh grade B or C). * Ascites and/or relevant intra-hepatic biliary tract dilatation. * Mental conditions rendering the patient incapable to understand the nature, scope, and consequences of the study.