ESR1 and breast cancer: Oncotype DX [14], Endopredict [13], and RecurIndex [15–17] are such genomic tests that utilize potential breast cancer genetic predictors suitable for patients that are recently diagnosed with early stage, estrogen receptor-positive (ER+) or progesterone receptor-positive (PR+), and Human epidermal growth factor receptor 2-negative (HER2-) breast cancer.