While each of these alterations offers a biologically plausible therapeutic target (e.g., RET inhibitors for RET-fusion tumors, pan-ERBB inhibition for NRG1-fusion cancers, MDM2 inhibitors for MDM2-amplifications and PARP inhibition for BRCA1/2-mutations), to date evidence in BTC is largely limited to preclinical data, case reports or very small patient series. This evidence concerns the gene MDM2 and cancer.