KRAS and BRAF Mutations in Stage II and III Colon Cancer: A Systematic Review and Meta-Analysis

Background KRAS and BRAF mutations are well-established predictive and prognostic factors in metastatic colorectal cancer; however, their impact in the adjuvant setting has not yet been established. Methods We performed a meta-analysis of adjuvant phase III trials in patients with stage II and III colon cancer with available data on the impact of KRAS or BRAF mutations on both disease-free survival (DFS) and overall survival (OS). Trials were subgrouped based on whether adjustment for microsatellite instability (MSI) was performed and the subgroup effect was analyzed through a meta-regression. To increase the precision of the estimates, a joint DFS-OS (so-called multivariate) meta-analysis was performed. All statistical tests were 2-sided. Results Nine trials were selected (QUASAR 2, PETACC-8, N0147, CALGB-89803, NSABP-C07, NSABP-C08, PETACC-3, QUASAR, MOSAIC) including a total of 10 893 patients. In the primary meta-analysis, KRAS mutation was associated with poor DFS (pooled hazard ratio [HR] = 1.36, 95% confidence interval [CI] = 1.15 to 1.61, P < .001) and OS (pooled HR = 1.27, 95% CI = 1.03 to 1.55, P = .03) and BRAF mutation was also associated with poor DFS (pooled HR = 1.33, 95% CI = 1.00 to 1.78, P = .05) and OS (pooled HR = 1.49, 95% CI = 1.31 to 1.70, P < .001). The effect of the mutations on outcome was enhanced in the MSI-adjusted subgroup for both the KRAS mutation (pooled HR for DFS = 1.43, 95% CI = 1.15 to 1.79, P = .001; and pooled HR for OS = 1.33, 95% CI = 1.03 to 1.71, P = .03) and the BRAF mutation (pooled HR for DFS = 1.59, 95% CI = 1.22 to 2.07, P = .001; and pooled HR for OS = 1.67, 95% CI = 1.37 to 2.04, P < .001). The interaction between BRAF and MSI adjustment was statistically significant for DFS (P-interaction = .02). This interaction was even more pronounced in the DFS-OS multivariate meta-analysis. Conclusions Both KRAS and BRAF mutations were statistically significantly associated with both DFS and OS, with the mutation effect being enhanced by MSI adjustment. Effective adjuvant treatment for microsatellite-stable BRAF or KRAS-mutated colon cancer represents an unmet clinical need, and exploring the use of recently available BRAF and KRAS inhibitors in this setting would be highly desirable.

Automated summary

KRAS and BRAF mutations are significantly associated with both DFS and OS in patients with colon cancer in the adjuvant setting, and their impact is enhanced by MSI adjustment. Effective adjuvant treatment for patients with microsatellite-stable BRAF or KRAS-mutated colon cancer is needed, and exploring the use of available BRAF and KRAS inhibitors in this setting is desirable.