Development and Validation of a 15-gene Expression Signature with Superior Prognostic Ability in Stage II Colorectal Cancer

Currently, there is no consensus about the use of adjuvant chemotherapy for patients with stage II colorectal cancer. Here, we aimed to identify and validate a prognostic mRNA expression signature for the stratification of patients with stage II colorectal cancer according to their risk for relapse. First, publicly available mRNA expression profiling datasets from 792 primary, stage II colorectal cancers from six different training cohorts were analyzed to identify genes that are consistently associated with patient relapse-free survival (RFS). Second, the identified gene expression signature was experimentally validated using NanoString technology and computationally refined on primary colorectal cancer samples from 205 patients with stage II colorectal cancer. Third, the refined signature was validated in two independent publicly available cohorts of 166 patients with stage II colorectal cancer. Bioinformatics analysis of training cohorts identified a 61-gene signature that was highly significantly associated with RFS (HR = 37.08, P = 2.68*10-10(6), sensitivity = 89.29%, specificity = 89.61%, and AUC = 0.937). The experimental validation and refinement revealed a 15-gene signature that robustly predicted relapse in three independent cohorts: an in-house cohort (HR= 20.4, P= 8.73*10(-23), sensitivity= 90.32%, specificity = 80.99%, AUC = 0.812), GSE161158 (HR = 5.81, P = 3.57*10(-4), sensitivity = 64.29%, specificity = 81.67%, AUC = 0.796), and GSE26906 (HR = 7.698, P = 7.26*10(-8), sensitivity = 61.54%, specificity = 78.33%, AUC = 0.752). In the pooled training cohort, the 15-gene signature (HR = 4.72, P= 7.76*10(-25), sensitivity= 75%, specificity= 67.44%, AUC= 0.784) was superior to the Oncotype DX colon 7-gene signature (HR = 2.698, P = 6.3*10(-8), sensitivity = 62.16%, specificity = 55.5%, AUC = 0.633). We report the identification and validation of a novel mRNA expression signature for robust prognostication and stratification of patients with stage II colorectal cancer, with superior performance in the analyzed validation cohorts when compared with clinicopathologic biomarkers and signatures currently used for stage II colorectal cancer prognostication.