To show for the first time that the correlation between ESR1 expression and EERES is important for endocrine therapy responsiveness, we analyzed the survival of ER-positive/HER2-negative breast cancer patients (n = 436) using tumor sample data from the TCGA Pan-Cancer Atlas and developed an algorithm to select patients with better survival by selecting patients based on both their ESR1 expression and EERES. This evidence concerns the gene ESR1 and neoplasm.