ESR1 and cancer: The phenomenon is supported by the comparison of survival populations from stage-matched patients in TCGA and clinical trials, where patient survival from clinical trials was substantially lower.27 Patients with advanced cancers may have higher incidences of mutations associated with other forms of treatment resistance, such as EGFR T790M and ESR1 mutations.28 The potentially unique molecular features in patients with advanced, chemotherapy-resistant cancers may represent one factor that contributes to the low success rate of the matched targeted therapy approach.