MTHFR and colorectal cancer: However, in multiple prognostic studies, statistical association of the MTHFR Glu429Ala polymorphism with response to treatment with 5-FU based chemotherapy in colorectal cancer patients was not detected [25], [26], [43]–[49] suggesting that MTHFR Glu429Ala polymorphism may not affect the efficacy of 5-FU based treatments.