Compositions/methods for employing fresh-frozen or FFPE colon cancer tissue in left side colon cancer (LCC) and right-side colon cancer (RCC) disease patients for risk of relapse assessment/stratification is provided (3 strata and a 4 strata methodology). An RCC gene panel of 4 genes (FAM69A, CDX2, FAM84A, ITGA3), and 9 genes (FAM69A, CDX2, ITGA3, FAM84A, ITPRIP, RAB3B, SMAD3, PCSK5, MMP28), is provided. An LCC gene panel of 4 genes (NOX4, WNT5A, MMP3, IBSP), and a 9 genes (MMP3, WINT5A, NOX4, IBSP, SLC16A6, CYPIBI, TFAP2C, MATN3, ANKRD6), is provided. A microchip-based clinical tool, and a kit including a microchip, is presented. The invention also describes a computer-implemented method for assessing relative risk of relapse in LCC and/or RCC disease. An individual patient scoring method that presents a continuous stratification score useful in the post-surgical colon cancer management of LCC and/or RCC patient is also presented.