The impact of primary tumour location in patients undergoing hepatic resection for colorectal liver metastasis.

Background: Primary tumour location has long been debated as a prognostic factor in colorectal cancer patients with liver metastases (CRLM) undergoing liver resection. This retrospective study was conducted to clarify the prognostic value of tumour location after radical hepatectomy for CRLM and its underlying causes.

Methods: We retrospectively analysed clinical data from 420 patients with CRLM whom underwent liver resection between January 2002 and December 2015. Right-sided (RS) tumours include tumours located in the cecum, ascending colon, and transverse colon, and left-sided (LS) tumours include those located in the splenic flexure, descending colon, sigmoid colon, and rectum.

Results: Both overall survival (OS) and disease-free survival (DFS) were similar between patients with RS and LS primary tumours (5-year OS: 46.5% vs 38.3%, P = 0.699; 5-year DFS: 29.1% vs 22.4%, P = 0.536). Specifically, RAS mutation rate was significantly higher in patients with RS tumours (P = 0.007). Subgroup analysis showed that the RAS mutation on the LS and RS tumours have different prognostic impact for CRLM patients on long-term survival after hepatic resection (RS, OS: P = 0.437, DFS: P = 0.471; LS, OS: P < 0.001, DFS: P = 0.002). The multivariable analysis showed that RAS mutant is an independent factor influencing OS in patients with LS primary tumour only.

Conclusions: The site of the primary tumour has no significant impact on the long-term survival in patients with CRLM undergoing radical surgery. However, prognostic value of RAS status differs depending on the site of the primary tumour.