PRELUDE-1 (Prospective Evaluation of Radiotherapy-induced Biologic Effects in Colorectal Cancer Oligometastatic Patients with LUng-limited Disease: Evolution of Cancer Genetics and Regulatory Immune Cells)

Inclusion Criteria:

* Age \<80 years
* Cytological or histological diagnosis of colorectal adenocarcinoma
* Two or three asymptomatic lung nodules smaller than 25 mm
* Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or 1
* Available Formalin Fixed Paraffin Embedded (FFPE) of resected primary tumor
* Negative pregnancy test for all potentially childbearing women
* Patient candidates to SBRT

Exclusion Criteria:

* Previous systemic anti-tumor treatments (allowed treatment with capecitabine or fluorouracil and radiotherapy in the neoadjuvant setting of rectal tumors with therapy terminated at least 6 months before)
* Neutrophils \<2000/mm³ or platelets \<100.000/mm³ or hemoglobin \<9 g/dl; serum creatinine level\> 1.5 times the maximum normal value; GOT and/or GPT \>5 times the maximum normal value and/or bilirubin level \>3 times the maximum normal value
* Previous or concomitant malignant neoplasms (excluding basal or spinocellular cutaneous carcinoma or in situ carcinoma of the uterine cervix)
* Active or uncontrolled infections
* Other concomitant uncontrolled diseases or conditions contraindicating the study drugs at clinician evaluation
* Presence of brain metastases
* Refusal or inability to provide informed consent
* Impossibility to guarantee follow-up