Evaluating whether KRAS/BRAF mutation status, anaemia and obstruction are associated with recurrence and mortality in non-metastatic colorectal cancer.

Background: KRAS and BRAF testing is currently recommended in metastatic colorectal cancer. There is evidence that KRAS and BRAF mutation status may act as a prognostic biomarker in patients with non-metastatic colorectal cancer. Data is limited on whether KRAS and BRAF mutation status impacts recurrence and mortality in patients with non-metastatic colorectal cancer.

Methods: A retrospective cohort study was conducted in a tertiary hospital examining outcomes in patients who had KRAS and BRAF testing for colorectal cancer in 2017. Primary outcomes were all-cause mortality and recurrence. Multivariable analysis for both outcomes, used cause specific Cox proportional hazards models with KRAS/BRAF status as exposure. For time to recurrence, a sensitivity analysis was performed with a weighted Fine-Grey model with death as a competing risk.

Results: KRAS mutation status was not associated with all-cause mortality (average Hazard Ratio (aHR) = 0.78, 95% CI 0.28-2.21) or recurrence (aHR = 0.96, 95% CI 0.32-2.86). BRAF mutation status was not associated with time to all-cause mortality (aHR = 3.06, 95% CI 0.79-11.8) or recurrence (aHR = 0.94, 95% CI 0.13-6.57). Increased risk of recurrence was significantly associated with large bowel obstruction (aHR = 2.73, 95% CI 1.16-6.45) and anaemia (aHR = 3.39, 95% CI 1.06-10.8) at time of surgery.

Conclusion: This study did not demonstrate an association between KRAS and BRAF mutations and all-cause mortality or recurrence. A significantly increased risk of cancer recurrence was found in patients with large bowel obstruction and in patients with anaemia at time of surgery. Anaemia should be promptly investigated and corrected prior to colorectal cancer surgery.