The results showed that HR+/HER2− breast cancer samples with high CEACAM6 expression had significantly elevated predicted IC50 values for several commonly used chemotherapeutic agents, including cyclophosphamide, epirubicin, paclitaxel, and 5-fluorouracil, as well as for endocrine therapies such as tamoxifen and fulvestrant. The gene discussed is CEACAM6; the disease is breast carcinoma.