Noninvasive Detection of Activating Estrogen Receptor 1 (ESR1) Mutations in Estrogen Receptor–Positive Metastatic Breast Cancer

Abstract

BACKGROUND Activating mutations in the estrogen receptor 1 (ESR1) gene are acquired on treatment and can drive resistance to endocrine therapy. Because of the spatial and temporal limitations of needle core biopsies, our goal was to develop a highly sensitive, less invasive method of detecting activating ESR1 mutations via circulating cell-free DNA (cfDNA) and tumor cells as a “liquid biopsy.” METHODS We developed a targeted 23-amplicon next-generation sequencing (NGS) panel for detection of hot-spot mutations in ESR1, phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA), tumor protein p53 (TP53), fibroblast growth factor receptor 1 (FGFR1), and fibroblast growth factor receptor 2 (FGFR2) in 48 patients with estrogen receptor-α–positive metastatic breast cancer who were receiving systemic therapy. Selected mutations were validated using droplet digital PCR (ddPCR). RESULTS Nine baseline cfDNA samples had an ESR1 mutation. NGS detected 3 activating mutations in ESR1, and 3 hot-spot mutations in PIK3CA, and 3 in TP53 in baseline cfDNA, and the ESR1 p.D538G mutation in 1 matched circulating tumor cell sample. ddPCR analysis was more sensitive than NGS and identified 6 additional baseline cfDNA samples with the ESR1 p.D538G mutation at a frequency of <1%. In serial blood samples from 11 patients, 4 showed changes in cfDNA, 2 with emergence of a mutation in ESR1. We also detected a low frequency ESR1 mutation (1.3%) in cfDNA of 1 primary patient who was thought to have metastatic disease but was clear by scans. CONCLUSIONS Early identification of ESR1 mutations by liquid biopsy might allow for cessation of ineffective endocrine therapies and switching to other treatments, without the need for tissue biopsy and before the emergence of metastatic disease.

Liquid biopsy - emergence of a new era in personalized cancer care

“…Most of these changes have been identified by comparing the plasma samples of specific cancers with that of healthy volunteers. Some examples include the alterations in estrogen receptor 1 and erb-b2 receptor tyrosine kinase 2 (ERBB2) of breast cancer patients which were not seen in tissues, but have been detected in cfDNA [79][80][81]. Uehiro and colleagues [82] compared the methylation signatures of nearly 140 candidate genes in plasma samples to detect early breast cancer in patients.…”

Application of Digital PCR in Detecting Human Diseases Associated Gene Mutation

“…Accordingly, ddPCR monitoring of recurrent ESR1 mutations in cfDNA is a practical method to predict estrogen therapy response. Its higher sensitivity has been confirmed to have a detection limit of 0.05% [25] compared with 1% in multiplex allele-specific and realtime PCR [26] and 3.1% in NGS [27].…”

Liquid Biopsy in Metastasized Breast Cancer as Basis for Treatment Decisions

“…Beyond ctDNA detection in the plasma of cancer patients in order to monitor disease dynamics, some groups were able to trace ctDNA mutations relevant to anticancer treatment resistance [38,39,40]. Murtaza et al [38] demonstrated in their study on 6 patients with advanced ovarian, breast and lung cancers that a high incidence of specific ctDNA alterations is associated with acquired drug resistance: A truncating mutation in the gene coding for mediator complex subunit 1 (MED1) was found in an MBC patient with progressive disease following treatment with tamoxifen and trastuzumab, and a splicing mutation in the growth arrest-specific 6 (GAS6) gene was identified in the same MBC patient following subsequent treatment with lapatinib.…”