This includes, for instance, endocrine therapy as a first-line intervention for ER+/HER2− breast cancer, targeted therapy for HER2+ breast cancer, chemotherapeutic protocols, radiation performance, and surgical removal of metastatic lesions, which could result in misestimation of the associations between current treatment options and survival benefits as well as ignorance of the influence of some new treatments, such as immunotherapy, PARP inhibitors, and PI3K-AKT inhibitors on survival benefits. The gene discussed is ESR1; the disease is breast cancer.