In clinical practice, the choices of different standard chemotherapeutic agents and regimens made by physicians depend upon their assessments of the clinicopathological characteristics of patients, including tumor sizes, tumor grades, estrogen receptor (ER), progesterone receptor (PR), lymph nodes (LNs), underlying comorbidities in patients, and the potential toxicities of the different chemotherapy regimens. This evidence concerns the gene ESR1 and neoplasm.