However, secondary kinase mutationscausing resistance to tyrosine kinase inhibitors (TKIs) frequentlyoccur in urothelial cancers and cholangiocarcinoma.10,11 Also, TKIs have been shown to have limited efficacy in breast cancerdespite FGFR1 overexpression,12 probablybecause these cancers are not sufficiently oncogene-addicted to theFGFR1 signal. This evidence concerns the gene FGFR1 and cancer.