Does KRAS mutation status impact the risk of local recurrence after R1 vascular resection for colorectal liver metastasis? An observational cohort study

Introduction: R0 margin is the standard in the surgical treatment of colorectal liver metastases (CLM). Recently R1 surgery, at least that enabling CLM vessel-detachment (Rlvasc), seems comparable to R0. As a possible background of that biologic factors could play some role. Among them, KRAS has been investigated in the present study. Methods: Patients who underwent curative surgery for CLM between 2008 and 2016 were identified. R0, Rlvasc and parenchymal R1 (R1 par; tumor exposure once dissected from the parenchyma) resections with known KRAS status were analyzed. Results: Of 1000 resection areas in 340 patients, 654 (65%) R0, 98 (10%) Rlvasc and 248 (25%) R1par. In mutated KRAS (mKRAS), local recurrence (LR) was similar between R0 and Rlvasc (per-patient 4,8% vs. 2%, p = 0.628; per-area 2,1% vs. 1,9%, p = 0.940), while higher in Rlpar (per-patient 25,4% and per-area 19,5%; p < 0.001 for both). In wild-type KRAS (wtKRAS), R0 had less LR compared to Rlvasc (per-patient 7,6% vs 14,6%, p = 0.335; per-area 3,1% vs 13,3%, p = 0.012) and Rlpar (per-patient 18,3%, p = 0.060; perarea 9,9%, p = 0.013). KRAS did not impact LR in R0 (per-patient 7,6% vs. 4,8%, p = 0.491; per-area 3,1% vs. 2,1%, p = 0.555), while wtKRAS Rlpar had less LR compared to mKRAS Rlpar (per-patient 18,3% vs 25,4%, p = 0.404; per-area 9,9% vs 19,5%, p = 0.048). Inversely, LR was increased in wtKRAS Rlvasc compared to mKRAS Rlvasc (per-patient 14,6% vs 2%, p = 0.043; per-area 13,3% vs 1,9%, p = 0.046). Conclusion: KRAS status does not impact LR risk in R0 resection. Inversely, Rlvasc vs Rlpar LR risk is reduced in mKRAS, and increased in wtKRAS. If confirmed these results are of note. (C) 2019 Published by Elsevier Ltd.