The trial is a monocentric prospective, randomised controlled, unblinded, parallel-group superiority trial of Stereotactic Body Radiation Therapy (SBRT) versus Microwave Ablation (MWA) for the curative treatment of inoperable colorectal liver metastases. Patients will be randomised on an equal basis to either SBRT or MWA. The two modality treatments (SBRT versus MWA) will be evaluated for short- and longer-term outcomes. The key short-term outcomes will include assessment of local response rate and acute toxicity. Longer-term outcomes will concentrate on oncological aspects of the disease with analysis of disease-free and overall survival and local recurrence rates at 3-year follow-up.