The primary effects of the covariates, which include the age of the breast cancer patient, patient education level, place of residence, marital status, pre-existing comorbidity, axillary node status, estrogen receptor, tumor size, body mass index at diagnosis, stage of cancer, baseline treatment, histologic grade, number of positive lymph nodes involved, and type of hormone used, were taken into consideration as potential predictors for the variable of interest. The gene discussed is ESR1; the disease is cancer.