Another fluoropyrimidine, namely capecitabine (trade name Xeloda), was rationally designed to mimic the continuous infusion of 5FU (Hoff et al. 2001) and is an oral 5FU prodrug used in the treatment of metastatic colon and breast cancers (Dean and Kane 2016b), including metastasis of HER2-positive breast cancer to the brain (Franchino et al. 2018). Here, ERBB2 is linked to breast cancer.