MTHFR and colorectal carcinoma: Therefore, in this study, five major variants in three genes, namely CDA Lys27Gln, CDA Ala70Thr, TP S471L, MTHFR C677T, and MTHFR A1298C, were investigated and correlated to assess the effect of such variations on CRC development in patients treated with capecitabine (Xeloda®).