The BRAF V600E mutation is an independent prognostic factor for survival in stage II and stage III colon cancer patients

Patients and methods: Stage II colon carcinoma patients (n = 106) treated with surgery only and 258 stage III patients all adjuvantly treated with 5-fluorouracil chemotherapy were included. KRAS mutations in codons 12 and 13, V600E BRAF mutation and MSI status were determined. Results: Older patients (P < 0.001), right-sided (P = 0.018), better differentiated (P = 0.003) and MSI tumors (P < 0.001) were significantly more frequent in stage II than stage III. In both groups, there was a positive association between mutated BRAF and MSI (P = 0.001) and BRAF mutation and right-sided tumors (P = 0.001). Mutations in BRAF and KRAS were mutually exclusive. In a multivariate survival analysis with pooled stage II and stage III data, BRAF mutation was an independent prognostic factor for overall survival (OS) and cancer-specific survival [hazards ratio (HR) = 0.45, 95% confidence interval (CI) 0.25-0.8 for OS and HR = 0.47, 95% CI 0.22-0.99]. KRAS mutation conferred a poorer disease-free survival (HR = 0.6, 95% CI 0.38-0.97). Conclusions: The V600E BRAF mutation confers a worse prognosis to stage II and stage III colon cancer patients independently of disease stage and therapy.