Supplementary Material for: A Validation Study for Recurrence Risk Stratification of Stage II Colon Cancer Using the 55-Gene Classifier

<b><i>Introduction:</i></b> DNA microarrays, such as the consensus molecular subtype (CMS) classification using &gt;600 genes, are used to predict cancer patient prognosis. We recently constructed a simple 55-gene classifier (55GC) system to risk stratify colon cancer (CC). <b><i>Objective:</i></b> Here, we validate the 55GC specifically for stage II CC and compare it with CMS categories. <b><i>Methods:</i></b> Tissue sections from 232 stage II CC patients who underwent curative surgery without adjuvant chemotherapy between 2009 and 2012 were subjected to DNA microarray analysis. <b><i>Results:</i></b> Based on the 55GC, patients were classified into microsatellite instability-like (27%), chromosomal instability-like (41%), and stromal (32%) subtypes with 5-year relapse-free survival (RFS) rates of 88.5, 83.3, and 71.2%, respectively (stromal vs. others: <i>p</i> = 0.0049). Multivariate analysis by Cox’s proportional hazard model revealed that the stromal subtype, pT4, and the number of lymph nodes examined (&lt;12) were independent poor prognostic factors. The overall concordance rate between 55GC and CMS was 72%, and 5-year RFS rates of patients with CMS1, CMS2, CMS3, and CMS4 cancers were 100, 85.5, 92.3, and 73.0%, respectively (<i>p</i> = 0.0113). <b><i>Conclusions:</i></b> We conclude that the 55GC is a useful and reproducible grading system for stage II CC recurrence risk stratification.