Background: Colorectal liver metastases attached major intrahepatic vessels has been considered to be risk factor for survival outcome after liver resection. The present study aimed to clarify the outcomes of R1 surgery (margin<1mm) in CRLM patients, distinguishing parenchymal margin R1 and attached to major intrahepatic vessels R1.
Methods: In the present study, 283 CRLM patients who evaluated to be attached to major intrahepatic vessels initially, underwent liver resection following preoperative chemotherapy. They were assigned to one of the following groups: R0 (n=167), R1 parenchymal (n=58) and R1 vascular (n=58). We analyzed the survival outcomes and local recurrence rates in each group.
Results: Overall, 3- and 5-year OS rates after liver resection were 53.0% and 38.2% (median OS 37 months). Five-year OS was higher in patients with R0 than R1p (44.9%% vs. 26.3%, p=0.009), whereas there was no significant difference from patients with R1v (34.3%, p=0.752). In the multivariable analysis, preoperative chemotherapy>4 cycles, CRS 3-5, RAS mutation, R1p and CA199>100IU/ml were identified as independent predictive factors of OS (p<0.05). There was no significant difference for local recurrence among three groups.
Conclusion: R1 parenchymal resection was independent risk factor for CRLM. R1 vascular surgery achieves outcomes equivalent to R0 resection. Non-anatomic liver resection for CRLM attached to intrahepatic vessels can be pursued to increase patient resectability by preoperative chemotherapy.