Analysis of tumor sizes in mice with the HR+/HER2-low breast cancer subtype revealed marked differences among the control (normal saline), CDK4/6 inhibitor + endocrine therapy, and triple combination (neratinib + CDK4/6 inhibitor + endocrine therapy groups (P < 0.05, P < 0.01). This evidence concerns the gene ERBB2 and breast carcinoma.