Most of the studies on MTHFR polymorphisms and upper gastrointestinal cancer could not reproduce the association of response with fluoropyrimidine based chemotherapy having been described for other cancer types, mainly advanced colon carcinoma [45,56,57], apart from one Chinese study for the TT genotype of the MTHFR C677T polymorphism and response [54]. Here, MTHFR is linked to cancer.