PIK3CA and colorectal cancer: To verify the independent prognostic value of NDRG4 mRNA expression on disease-free survival of patients with colorectal cancer, cox proportional hazards model adjusted for sex, age, tumor location, tumor size, differentiation status, vascular invasion, TNM stage, KRAS, BRAF and PIK3CA mutations and MSI status was utilized to control for other prognostic factors.