ESR1 and breast cancer: Further, Aft et al.[14] demonstrated that DTC-free BC patients treated with ZOL (4 mg every 3 weeks) were more likely to remain DTC free at 3 months (P = 0.03), and that the subset of patients with estrogen receptor-negative and epidermal growth factor receptor-2–negative disease were more likely to have pathologic complete response with ZOL versus no ZOL.