There is evidence that the orally active 5-fluoracil prodrug, capecitabine, is directly effective against BCBM—metabolites can be detected in BM surgical samples from BC patients given a single pre-operative dose [14], objective CNS responses to monotherapy have been observed in a small case series [15] and it enhances the clinical benefit of HER2-targeted therapy [16,17]. This evidence concerns the gene ERBB2 and breast cancer.