To further explore the prognostic value of the HER2DX risk score in the adjuvant setting, we interrogated three publicly available breast cancer datasets (i.e., TCGA,22 METABRIC23 and SCAN-B25), which include clinical data, overall survival (OS) outcome and gene expression data for a total of 810 patients with early-stage HER2-positive breast cancer (Table S1). This evidence concerns the gene ERBB2 and breast cancer.