A Study of Single Fraction Stereotactic Body Radiation Therapy (SBRT) Guided by Magnetic Resonance Imaging (MRI) in People With Liver Metastasis From Colorectal Cancer

Inclusion Criteria: * Age ≥18 * Histologically confirmed colorectal carcinoma and evidence of liver metastasis on imaging * ECOG 0-2 * \<=3 liver lesions measurable on contrast enhanced diagnostic MRI with combined size (sum of longest diameters) \< 7 cm, and individual size \< 5cm. (Subsequent simulation scans will not be used for eligibility assessment. In case of significant change in size exceeding 1cm, the individual participants can continue on the protocol provided all normal tissue contraints are met during planning). * Lesion location at least ≥ 2 cm of main, right and left portal vein on the baseline diagnostic MRI. (Subsequent simulation scans will not be used for eligibility assessment. In case of significant change in the distance between the lesion edge and critical structure exceeding 1cm, the individual participants can continue on the protocol provided all normal tissue contraints are met during planning ). * Lesion location at least ≥ 1.5 cm of luminal gastrointestinal tract (stomach, small and large bowel). (Subsequent simulation scans will not be used for eligibility assessment. In case of significant change in the distance between the lesion edge and critical structure exceeding 1cm, the individual participants can continue on the protocol provided all normal tissue contraints are met during planning). * Lesion location ≥ 0.5 cm of diaphragm * Preserved liver function as defined by: * Albumin \> 2 g/dl * \< AST/ ALT ≤ 5 x ULN * Total Bilirubin ≤ 1.5 x UL * Negative serum pregnancy test within 14 days prior to simulation and MRgRT for women of childbearing potential * Any prior systemic or hepatic artery intraarterial pump (HAIP) chemotherapy is permitted with a washout of 2 weeks * Any prior treatment with FDA-approved or investigational biologics or novel molecularly targeted therapies, including oral or IV formulations, are permitted with a washout of 1 weeks or 4 half-lives, which ever is longer * Extrahepatic disease outside the liver is permitted * Prior liver resection is permitted provided there is enough liver parenchyma to meet normal tissue contraints * Prior liver-directed RT is permitted provided departmental normal tissue constraints for re-irradiation can be met * Review by HBP DMT prior to enrollment Exclusion Criteria: * Any history of cirrhosis * History of hepatic radioembolization or selective internal radiation therapy (SIRT) * History of inflammatory bowel disease that precludes liver RT (at the discretion of the treating radiation oncologist). * Current pregnancy or breastfeeding * Men or women not using effective contraception. * Contraindication to or inability to undergo an MR scan, including, but not limited to the history of MR unsafe implants, any implanted cardiac pacemakers or deffibrilators, history of claustrophobia, and contraindications to Gd-EOB-DTPA contrast agent. * Concurrent anti-neoplastic therapy of any kind defined as receipt within 1 week of RT administration