In this study, all 52 patients were resistant to standard treatment, the median number of prior chemotherapy lines was 2(0-5), and the cohort included patients with TNBC and ER-positive/HER2-negative breast cancer with resistance to chemotherapy and endocrine therapy and patients with HER2-positive breast cancer who progressed on at least one anti-HER2 agent. This evidence concerns the gene ESR1 and breast cancer.