The interplay of KRAS mutational status with tumor laterality in non-metastatic colorectal cancer: An international, multi-institutional study in patients with known KRAS, BRAF, and MSI status

Background: Although the prognostic relevance of KRAS status in metastatic colorectal cancer (CRC) depends on tumor laterality, this relationship is largely unknown in non-metastatic CRC. Methods: Patients who underwent resection for non-metastatic CRC between 2000 and 2018 were identified from institutional databases at six academic tertiary centers in Europe and Japan. The prognostic relevance of KRAS status in patients with right-sided (RS), left-sided (LS), and rectal cancers was assessed. Results: Of the 1093 eligible patients, 378 had right-sided tumors and 715 had left-sided tumors. Among patients with RS tumors, the 5-year overall (OS) and recurrence-free survival (RFS) for patients with KRASmut versus wild-type tumors was not shown to differ significantly (82.2% vs. 83.2% and 72.1% vs. 76.7%, respectively, all p >.05). Among those with LS tumors, KRAS mutation was associated with shorter 5-year OS and RFS on both the univariable (OS: 79.4% vs. 86.1%, p =.004; RFS: 68.8% vs. 77.3%, p =.005) and multivariable analysis (OS: HR: 1.52, p =.019; RFS: HR: 1.32, p =.05). Conclusions: KRAS mutation status was independently prognostic among patients with LS tumors, but this association failed to reach statistical significance in RS and rectal tumors. These findings confirm reports in metastatic CRC and underline the possible biologic importance of tumor location.