The prognostic significance of KRAS and BRAF mutation status in Korean colorectal cancer patients.

Background: BRAF and KRAS mutations are well-established biomarkers in anti-EGFR therapy. However, the prognostic significance of these mutations is still being examined. We determined the prognostic value of BRAF and KRAS mutations in Korean colorectal cancer (CRC) patients.

Methods: From July 2010 to September 2013, 1096 patients who underwent surgery for CRC at Seoul St. Mary's Hospital were included in the analysis. Resected specimens were examined for BRAF, KRAS, and microsatellite instability (MSI) status. All data were reviewed retrospectively.

Results: Among 1096 patients, 401 (36.7%) had KRAS mutations and 44 (4.0%) had BRAF mutations. Of 83 patients, 77 (92.8%) had microsatellite stable (MSS) or MSI low (MSI-L) status while 6 (7.2%) patients had MSI high (MSI-H) status. Patients with BRAF mutation demonstrated a worse disease-free survival (DFS, HR 1.990, CI 1.080-3.660, P = 0.02) and overall survival (OS, HR 3.470, CI 1.900-6.330, P < 0.0001). Regarding KRAS status, no significant difference was noted in DFS (P = 0.0548) or OS (P = 0.107). Comparing the MSS/MSI-L and MSI-H groups there were no significant differences in either DFS (P = 0.294) or OS (P = 0.557).

Conclusions: BRAF mutation, rather than KRAS, was a significant prognostic factor in Korean CRC patients at both early and advanced stages. The subgroup analysis for MSI did not show significant differences in clinical outcome. BRAF should be included in future larger prospective biomarker studies on CRC.