Seraseq® ctDNA ESR1 MixThe ESR1 gene is frequently mutated in metastatic breast cancer (MBC), with 15 50% of all metastatic breast cancer patients harboring ESR1 mutations. ESR1 mutations develop in response to selection pressure during treatment and are typically undetectable in the primary tumor. The recent emergence and approval of drug therapy specific to ESR1 mutations in metastatic breast cancer have led to the updated guidance to monitor MBC patients for mutations in