For Chinese population, a study with 152 MBC cases reported that tumor size, radical mastectomy, and hormone therapy were risk factors for both OS and DFS in MBC cases (31), while another study of 77 Chinese MBC cases only found that M stage was significant prognostic factor, and ER, PR, and HER2 status had no impact on OS of MBC (9). Here, ESR1 is linked to neoplasm.