In vivo isolation of circulating tumour cells using CellCollector and detection of gene mutations in different metastasis organ sites in breast cancer

Introduction: Metastasis is thought to result from tumour cell entry into the circulation and migration to distant organs, where the mutation landscape of metastatic breast cancer (MBC) may shift and vary. The genotypic features of circulating tumour cells (CTCs) typically differ from those of primary breast cancer (BC) cells. Gene mutation analysis of CTCs in MBC may benefit patients by identifying those amenable to specific therapies. Currently, CTCs are primarily isolated in vitro from small volumes of blood. The aim of this study was to isolate CTCs in vivo using CellCollector and screen for specific gene mutations in cells from different metastasis organ sites and molecular subtypes in MBC patients. Methods: In this study, we used a novel technology, CellCollector, to collect peripheral CTCs. Thirty MBC patients were enrolled, and 17 were analysed with next-generation sequencing (NGS) methods. Clinical characteristics were analysed along with CTC enumeration and detection rates. Whole-genome amplification (WGA) was used to amplify the CTC genomic DNA of 127 genes. Results: We isolated CTCs in vivo from 20 of 30 MBC patients (66.7%), with a median and mean (range) of 2 (0-15) CTCs. In non-cancer patients, no CTCs were detected. We analysed CTC enumeration and the detection rate in different clinical characteristic subgroups. We found that in their corresponding subgroups, patients younger than 45 years old, with brain metastasis, with three or more metastasis organ sites, or with HER2-positive subtypes had the highest CTC medians and means.As far as clinical characteristics were concerned, the number of CTCs seemed correlated with more advanced clinical characteristics. In the one metastasis organ, two metastasis organs and three or more metastasis organs subgroups, the CTC detection rates were 38.5% (5/13), 77.8% (7/9), and 100.0% (8/8), respectively. The CTC detection rate correlated with the number of metastasis organs; patients with more metastasis organ sites had higher CTC detection rates. We also found that different metastasis organs and molecular subtypes contain high-frequency mutation genes, and also contain unique gene mutations. Conclusions: In MBC, CellCollector can be used to collect intact CTCs, from which we can obtain gene mutation information. Different metastasis organs and molecular subtypes may have corresponding unique mutations, which may provide a basis for future gene therapy. Citation Format: Geng C, Li S, Yang S, Shi J, Ding Y, Gao W, Cheng M, Sun Y, Xie Y, Sang M. In vivo isolation of circulating tumour cells using CellCollector and detection of gene mutations in different metastasis organ sites in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-01-18.