Genetic biomarkers for left side colon cancer (LCC) (such as expression levels of an RNA transcript or expression product of NOX4, MMP3, or a combination) and right side colon cancer (RCC) (such as expression levels of an RNA transcript or expression product of CDCX2, FAM69A, or a combination), are disclosed. Methods for using the biomarkers in providing a prognosis of relapse-free survival probability in patients having LCC or RCC are also presented. Prognostic panels using gene expression values of the biomarkers are also presented. Computer implemented methods employing the biomarkers, and as well as for determining relapse-free survival probability in a patient having RCC or LCC are provided. A genetic method for classifying a colon cancer tissue as a RCC or as a LCC is also disclosed.