The investigator propose a prospective study using blood samples (liquid biopsy) of estrogen receptor (ER)-positive metastatic breast cancer (MBC) patients to understand the prevalence of estrogen receptor 1 (ESR1) mutation variants and the correlation with hormonal therapy (HT)-based treatment resistance in Asian ER-positive/human epidermal growth receptor-2 (HER2)-negative MBC population.
Name: Hormonal therapy-based treatments
Description: The percentage of each ESR1 LBD mutation variant in Asian ER-positive/HER2-negative MBC who had received at least one line of HT
Measure: The percentage of ESR1 LBD mutation variant Time: 12 monthsDescription: PFS of patients who are treated with everolimus plus HT with either ESR1 wild type or different Asian-specific prevalent ESR1 LBD mutation variants such as Y537C
Measure: Progression-free Survival (PFS) Time: 12 monthsCase-Only
There are 3 SNPs
For the second purpose, the investigator will specifically focus on patients with ESR1 Y537C mutation, while the results from patients with wild type ESR1 and patients with D538G or Y537S mutant will be severed as control for preliminary comparison. --- Y537C --- --- D538G ---
PFS of patients who are treated with everolimus plus HT with either ESR1 wild type or different Asian-specific prevalent ESR1 LBD mutation variants such as Y537C. --- Y537C ---
Metastatic Breast Cancer Breast Neoplasms The investigator will use next-generation targeted sequencing covering the entire ESR1 ligand-binding domain (LBD) region to understand 1. the spectrum and prevalence of specific ESR1 mutation variants in Asian women, and 2. the preliminary correlation of Asian-specific prevalent ESR1 LBD mutation variants such as Y537C with treatment efficacy. --- Y537C ---
For the second purpose, the investigator will specifically focus on patients with ESR1 Y537C mutation, while the results from patients with wild type ESR1 and patients with D538G or Y537S mutant will be severed as control for preliminary comparison. --- Y537C ---
For the second purpose, the investigator will specifically focus on patients with ESR1 Y537C mutation, while the results from patients with wild type ESR1 and patients with D538G or Y537S mutant will be severed as control for preliminary comparison. --- Y537C --- --- D538G --- --- Y537S ---