TYMS and colorectal cancer: A repeat polymorphism within the 5′ untranslated region (UTR), that alters TS expression was correlated with response and survival in colorectal cancer patients receiving 5-FU in several studies (Horie et al, 1995; Kawakami et al, 1999; Iacopetta et al, 2001; Pullarkat et al, 2001; Marsh et al, 2001).