In this large cohort study of patients with early-stage HR-positive, ERBB2-negative breast cancer, adjuvant chemotherapy use almost doubled in premenopausal women with node-positive tumors and a low to intermediate genomic risk but decreased for patients with node-negative tumors from 2019 to 2022, coinciding with the publication of the TAILORx and RxPONDER trials. This evidence concerns the gene ERBB2 and breast carcinoma.