Impact of microscopic incomplete resection for colorectal liver metastases on surgical margin recurrence: R1-Contact vs R1 < 1 mm margin width

Background: Several studies highlighted an inferior outcome of R1 resection for colorectal cancer liver metastases (CRLM); it is still unclear whether directly involved margins (R1-contact) are associated with a poorer outcome compared to R1 < 1 mm. The aim of this study is to analyze the impact on surgical margin recurrence (SMR) of R1-contact vs R1 < 1 mm patients.

Methods: Patients who underwent surgery for CRLM between 2009-2018 with both R1 resections on final histology were included and compared in terms of recurrence and survival. Factors associated with SMR were assessed by univariate and multivariate analysis.

Results: Out of 477, 77 (17.2%) patients showed R1 resection (53 R1-Contact and 24 R1 < 1 mm). Overall recurrence rate was 79.2% (R1 < 1 mm = 70.8% vs R1-contact group = 83%, P = .222). Median disease-free survival (DFS) and disease-specific survival (DSS) were significantly higher in R1 < 1 mm vs R1-contact group (93 vs 55 months; P = .025 and 69 vs 46 months; P = .038, respectively). The SMR rate was higher in R1-contact compared to R1 < 1 mm group (30.2% vs 8.3%; P = .036). At univariate analysis, age, number of metastases, open surgical approach, RAS status, and R1-contact were associated with SMR. At multivariate analysis, R1-contact margin was the only factor independently associated with higher SMR (OR = 5.6; P = .046).

Conclusions: R1-contact margin is independently associated with SMR after liver resection for CRLM. Patients with R1-contact margin will also experience poorer DFS and DSS.