Breast Cancer (ER/PR+)

    Actionable Target Abnormality Prevalence (%) Clinical Experience with Targeted Agent
    ESR1 Mutation 20–30* • Predicts resistance to aromatase inhibitors and associated with shorter survival (1)
    • Specific variants predict for lack of response to fulvestrant or everolimus (e.g., Y537S) (2,3)
    Fulvestrant (estrogen receptor downregulator):
    • In ESR1 mutants, PFS 5.7 vs. 2.6 mo for exemestane (4)
    ERBB2 (HER2) Mutation 2 • Typically exclusive with ERBB2 amplifications (5)
    • Kinase domain mutations predict response to TKIs (e.g., neratinib) (6)
    • Extracellular domain mutations predict for response/resistance to trastuzumab/pertuzumab (7)
    Other topics in Targets by Organ Site