In ER+/HER2- mBC
Test for ESR1m upon 1L progression to inform 2L treatment
Recommendations for testing
- Use liquid biopsy to test for ESR1 mutations upon progression on 1L ET1,2
- ctDNA can provide a real-time tumor biomarker profile through liquid biopsy2,3
- Archival tissue samples are not recommended for detecting ESR1 mutations4
– Due to their emergence following 1L ET + CDK4/6i, ESR1 mutations are rarely found in primary tumors
- Test for ESR1m at each progression if not detected previously, as ESR1 mutations may emerge upon repeated exposure to ET1,2
Abbreviations: 1L, first line; 2L, second line; CDK4/6i, cyclin-dependent kinase 4/6 inhibitor; ctDNA, circulating tumor deoxyribonucleic acid; ER+, estrogen receptor-positive; ESR1, estrogen receptor 1; ESR1m, estrogen receptor 1 mutation; ET, endocrine therapy; HER2-, human epidermal growth factor receptor 2-negative; mBC, metastatic breast cancer.
References: 1. Burstein HJ, DeMichele A, Somerfield MR, et al. Biomarker Testing and Endocrine and Targeted Therapy in Metastatic Breast Cancer Expert Panels. Testing for ESR1 mutations to guide therapy for hormone receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer: ASCO guideline rapid recommendation update. J Clin Oncol. 2023;41(18):3423-3425. 2. Russano M, Napolitano A, Ribelli G, et al. Liquid biopsy and tumor heterogeneity in metastatic solid tumors: the potentiality of blood samples. J Exp Clin Cancer Res. 2020;39(1):95. 3. Lee N, Park MJ, Song W, et al. Currently applied molecular assays for identifying ESR1 mutations in patients with advanced breast cancer. Int J Mol Sci. 2020;21(22):8807. 4. Spoerke JM, Gendreau S, Walter K, et al. Heterogeneity and clinical significance of ESR1 mutations in ER-positive metastatic breast cancer patients receiving fulvestrant. Nat Commun. 2016;7:11579.