Aim: To evaluate the clinicopathological features of colorectal cancer (CRC) with a v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) mutation and its molecular interaction with microsatellite instability (MSI) and v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) in patients with advanced CRCs. Methods: From October 2009 to December 2011, 141 patients with stage III (n = 51) or IV (n = 90) CRCs who were tested for the BRAF mutation at Severance Hospital were included. Among 141 patients, five were excluded due to follow-up loss. Therefore, 136 patients were included in the study. The clinicopathological data, MSI status, and KRAS/BRAF mutation status were reviewed retrospectively. In addition, to evaluating the value of BRAF mutation status, progression-free survival and overall survival in all patients were collected and compared between the BRAF wild-type group and BRAF mutation group. Results: Of 136 patients, 80 (58.8%) were male and the mean age was 59 years. BRAF and KRAS mutations were detected in 9.6% and 35.3% of patients, respectively. Only 4.3% of patients had MSI-high tumors and there were no MSI-high in tumors with a BRAF mutation. BRAF mutations tended to be more frequent in stage IV than in stage III (11.76% vs 5.88%, P = 0.370). Patients with a BRAF mutation had a lower incidence of KRAS mutation than those without (7.69% vs 38.21%, P = 0.033). Overall survival was significantly shorter in the BRAF mutation group than in the BRAF wild-type group both by univariate analysis (P = 0.041) and multivariate analysis (HR = 2.195; 95%CI: 1.039-4.640; P = 0.039), while progression-free survival was not different according to BRAF mutation status. Conclusion: CRCs with a BRAF mutation have distinct molecular features and resulted in a poor prognosis in Korean patients with advanced CRC.
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