Although there is no established predictive marker for response to AR-targeted therapy in breast cancer, Enza plus the aromatase inhibitor exemestane was shown to be effective in patients with ER-positive advanced breast cancers with a gene signature-based biomarker indicating AR activation [24], and both bicalutamide and enzalutamide showed efficacy in metastatic AR-positive triple-negative breast cancer (TNBC) [25, 26]. The gene discussed is ESR1; the disease is breast cancer.