We used multivariate Cox regression analysis to determine whether predictive capacity of BCSigLnc-12 was independent of other clinicopathological factors of breast cancer patients in the discovery cohort, test cohort-2 and test cohort-3 (no available clinicopathological information in test cohort-1), such as age, tumor size, tumor grade, estrogen receptor (ER) status and lymph node status. This evidence concerns the gene ESR1 and breast cancer.