In this study, colorectal cancer patients with initially resectable liver-only metastases, as prospectively confirmed by a local multidisciplinary team (MDT) according to predefined criteria, will be tested for RAS and BRAF tumor mutation status. Patients with gene mutant or right-sidedness will be randomised between anatomical resection (AR) or nonanatomical resection (NAR). The primary end-point is the relapse-free survival.

This study is a prospective, single-center, randomized control trial. The major including criteria are (1) Histologically confirmed colorectal cancer initially resectable liver-only metastases ; (2) patient has the opportunity to perform either anatomical resection (AR) or nonanatomical resection (NAR) surgery; (3) the number of metastasis is 1-3; (4) KRAS/NRAS/BRAF mutation or right-sidedness. Patients will be randomised between AR or NAR. Patients will be stratified for gene mutation and right-sidedness.

Based upon the segmental anatomy of the liver according to Couinaud system, AR is defined as the resection of one or more complete hepatic segments in our study, including bisegmentectomy, right hemihepatectomy, left hemihepatectomy, extended right hemihepatectomy, extended left hemihepatectomy, single segmentectomy, caudate lobectomy, or a combination thereof. NAR, also called as wedge resection, is defined as the resection of the tumor with a margin of normal parenchyma regardless of the hepatic anatomy.

The primary end-point is the relapse-free survival. The secondary end-points are postoperative complication, postoperative mortality, hospital length of stay, and overall survival.

Inclusion Criteria:

1. Age ≥ 18 and ≤ 75 years;
2. Histological proof of colorectal adenocarcinoma;
3. Resectable colorectal liver metastasis without detectable extrahepatic distant metastatic disease (determined by a local MDT);
4. Suitable for anatomical or nonanatomical liver resection (determined by a local MDT);
5. Number of metastasis is 1 to 3;
6. KRAS/NRAS/BRAF mutation or right-sidedness;
7. Performance Status (ECOG) 0~1;
8. Adequate hematological function: Neutrophils≥1.5 x109/l and platelet count≥100 x109/l; Hb ≥9g/dl (within 1 week prior to randomization);
9. Adequate liver and renal function: total bilirubin ≤2.0 mg/dl, serum transaminases ≤ 5x upper limit of normal(ULN), and serum creatinine ≤ 1.5x ULN and creatinine clearance ≥ 30 ml/min;
10. Written informed consent.

Exclusion Criteria:

1. Previous systemic treatment for metastatic disease;
2. Previous surgery for metastatic disease;
3. Extrahepatic metastases;
4. Unresectable primary tumor;
5. Major cardiovascular events (myocardial infarction, severe/unstable angina, congestive heart failure, CVA) within 12 months before randomisation;
6. Second primary malignancy within the past 5 years;
7. Acute or subacute intestinal obstruction;
8. Drug or alcohol abuse;
9. No legal capacity or limited legal capacity;
10. Pregnant or lactating women.