Colorectal cancer survival can be influenced by variable confounding factors, including geographic region, tumor stage, histologic type, or other underlying genetic mutations, such as P53[53] and DCC.[54] Second, the comparisons between KRAS codon 13 and codon 12 mutations were made indirectly using data generated from individual comparisons versus KRAS wild-type, because direct comparison data were not available. Here, KRAS is linked to colorectal cancer.