Abstract 4113: Discriminatory 11-plex assay designed to monitor estrogen receptor mutations using a novel, melt-analysis capable digital PCR platform

Abstract

Abstract In a large fraction of ER+/HER2- metastatic breast cancer (MBC) patients, treatment with aromatase inhibitors fails due to emerging resistance. A key mechanism of this resistance is associated with a limited set of missense mutations in the gene encoding for the estrogen receptor (ESR1). These mutations are primarily found in the ligand binding domain of the protein. They result in a constitutively active estrogen receptor, are infrequently found in primary tumors (<5%) and instead likely coincide with the emergence of an endocrine resistant phenotype. The occurrence of ESR1 mutations following treatment has varied from study to study depending on patient selection and method of detection, but prevalence may be as high as 50%. Because these patients require second line therapies as soon as possible, ESR1 mutations are an area of intense focus in research and clinical trials for ER+/HER2- breast cancer. Studies utilizing droplet digital PCR (ddPCR) assays have correlated an increase of ESR1 mutations in patient liquid biopsy samples with therapeutic resistance approximately 8 months prior to conventional methods, however the number of individual mutations evaluated in these studies was limited due to an inability to accurately and sensitively identify more than one individual mutated SNP allele within a single reaction. We have developed a multiplex digital PCR assay that utilizes melt-based probes to detect and discriminate between 10 unique, clinically relevant ESR1 mutations in circulating tumor DNA (ctDNA) samples while simultaneously quantifying total cell-free DNA (cfDNA). Designed for use with an innovative, array-based dPCR system, the assay requires a hands-on time of only 10-15 minutes and a total run time of 2.5 hours. This assay will allow breast cancer researchers to further refine our understanding of the role ESR1 mutations play in personalized treatment strategies for MBC. Citation Format: Jennifer N. Bernier, Johanna E. Takach, Tiffany Wang, Steve Gallagher, Robert Lin, Andrew Zayac, Paul Hung, Matthew Lesho, Douglas Whitman. Discriminatory 11-plex assay designed to monitor estrogen receptor mutations using a novel, melt-analysis capable digital PCR platform [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4113.