Low and Intermediate Risk OliGometastatic ColoREctal CancEr PatieNts Treated with Stereotactic ABlative Radiotherapy

Inclusion Criteria: * Age ≥18 years * Histologically confirmed CRC * Low and intermediate risk oligometastatic colorectal cancer with 1 to 3 metastases, candidate to I or II line systemic treatment (Low risk: 1 to 3 metastases and cumulative tumor volume smaller than 10 cm3; Intermediate risk: 1 to 3 metastases and cumulative tumor volume bigger than 10 cm3). * Controlled primary tumor regardless of primary surgery or primary systemic treatment * ECOG/WHO 0-2 * Life expectancy \> 6 months * Lesions ≤ 5 cm * Adequate organ function for the planned treatment according to local guidelines * For patients with liver metastases: no cirrhosis or hepatitis, and evidence of adequate hepatic function (Total bilirubin level \< 1.5 x institutional ULN; ALT and AST levels \< 3.0 x institutional ULN, GGT and alkaline phosphatase levels \< 3.0 x institutional ULN; INR and APTT levels \< 1.5 x institutional ULN, Albumin \> 2.5 mg/dL) * For patients with liver metastases: unresectable liver metastases (assessed by a surgeon, preferably hepatobiliary) or refusal of liver surgery before study screening. * If childbearing potential, willing to use an effective form of contraception throughout the duration of the study * Signed informed consent and willingness to follow the trial procedures Exclusion Criteria: * Age \< 18 years * Brain metastases * Having more than 3 metastases * Malignant pleural effusion or ascites * Unable to undergo imaging by either CT scan or MRI * Evidence of any other medical conditions (such as psychiatric illness, infectious diseases, neurological conditions, physical examination or laboratory findings) that may interfere with the planned treatment or affect patient compliance. * Pregnancy or breast-feeding