Abstract 1368: Simultaneous cell-free RNA PD-L1 expression and MSI from the same single-tube of blood in solid tumors (original) (raw)

Clinical Research (Excluding Clinical Trials), 2019

Abstract

Background: Liquid biopsy is a minimally invasive technique available in the clinic using next-generation sequencing (NGS) of plasma circulating cell-free DNA (cfDNA) and cfRNA. Here we report liquid biopsy results from solid tumors using the Circulogene Theranostics Personalized Gene Profile (CGP, 50-gene panel), as well as, microsatellite instability (MSI) testing. CGP uses proprietary in situ enrichment requiring minimal input volume of 20 uL plasma (cfDNA), 400 uL (cfRNA), and 100 uL buffy coat per case from the same single-tube of blood. Methods: cfRNA PD-L1 expression, MSI, and co-occurring cfDNA mutations were retrospectively compiled from CGP ordered at multiple centers. Ct value cutoff for 1 copy PD-L1 (positive) was 42. MSI was performed using paired buffy coat gDNA (normal) and plasma cfDNA (tumor) on 5 microsatellite mononucleotide markers, BAT-25, BAT-26, NR-21, NR-24 and MONO-27 (Promega; current an industry standard that has been used in KEYNOTE pembrolizumab trials) and analyzed by capillary electrophoresis genetic analyzer. Based on batched processing, Circulogene’s turnaround time (TAT) is 5 business days on average. Data was summarized and the correlation between PD-L1 and MSI was measured. Results: 397 patients (median age 67 years, range 27-96; 210 men: 187 women) underwent CGP testing for both PD-L1 and MSI (11/2017-10/2018). The majority of cancer types were lung (n=187), colorectal (n=43), breast (n=40), pancreatic (n=32), and prostate (n=30). 59/397 (14.9%) were PD-L1 positive, in the range of expected PD-L1 positivity across solid tumors. 110/397 (27.7%) were MSI-High (MSI-H). There was no correlation between PD-L1 and MSI results (r^2 Conclusions: Simultaneous cfRNA PD-L1 and MSI testing from the same single-tube blood is feasible in a liquid biopsy and their positivity has frequency in the expected range for solid tumors (Xang et al. Onco Targets Ther 2016, Zhang et al. AMP Conference 2018, Abstract ST009). Despite the low plasma sample input, there were no sample failures, suggesting CGP in situ enrichment is robust and has a rapid TAT. Assay results with linkage to clinical outcomes is warranted. Citation Format: Glen J. Weiss, Paul Walker, Dilek Aktas, Andrew Ford, Charmaine Brown, Chen-Hsiung Yeh, Nader Javadi. Simultaneous cell-free RNA PD-L1 expression and MSI from the same single-tube of blood in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1368.

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