Abstract 1387: Tracking minimal residual disease in post-operative cell-free DNA using MSK-ACCESS
Authors: Hasan Maysun M. , Patel Juber , Johnson Ian , Meng Fanli , Tam Grittney K. , Jing Xiaohong , Yang Julie L. , Brannon A. Rose , Gowtham Jayakumaran , Stephens Dennis P. , Diosdado Monica , Benayed Ryma , Zehir Ahmet , Chen Chin-Tung , Weiser Martin R. , Tsui Dana , Houck-Loomis Brian , Berger Michael 
Published: August 2019

Abstract
A noted clinical application for liquid biopsy is as a non-invasive method of detecting and monitoring of minimal residual disease (MRD) in patients with cancer. The low concentration of circulating tumor DNA in blood, especially in early stage cancers, however, complicates the detection of tumor-derived cell-free DNA. To address this challenge, we have developed MSK-ACCESS (Analysis of Circulating cfDNA to Examine Somatic Status), a custom NGS assay covering selected exons from 129 cancer related genes for high-sensitivity detection of somatic mutations from plasma. Using ultra-high depth sequencing, with duplex unique molecular indexing (UMI), unique dual sample barcodes, and background error suppression, MSK-ACCESS is able to detect low-frequency (0.1%) variants with high confidence. The design of MSK-ACCESS leverages our dataset of more than 30,000 tumors profiled by our institutional tumor sequencing assay, MSK-IMPACT, ensuring that the majority of patients harbor multiple mutations that can be tracked in plasma.
We have validated MSK-ACCESS using plasma samples collected from 40 healthy individuals and 70 cancer patients harboring a range of somatic mutations in 11 genes. Greater than 95% of mutations at allele fractions &gt;0.1% were empirically detected, and we established the performance characteristics of the assay through intra- and inter-assay reproducibility tests and dilution experiments. We have initiated clinical trials in multiple tumor types to evaluate the benefit of early therapeutic intervention in patients where MSK-ACCESS can detect circulating tumor DNA following surgery. Tumor mutations revealed by MSK-IMPACT in surgically resected specimens will be monitored at regular intervals as evidence of MRD. As a proof of concept, we have applied MSK-ACCESS to monitor variants known from tissue tumor sequencing in pre- and post-surgical cfDNA samples from 9 colon adenocarcinoma patients. All samples were sequenced to an average total depth of approximately 20,000X coverage and subsequently collapsed to consensus sequences exhibiting an average noise level less than 0.0006%. Circulating tumor DNA was detected in 66%(6/9) of the pre-surgical samples. Of these samples, ctDNA was also detected in 50% (3/6) of the post-surgical samples. Overall, this study shows that MSK-ACCESS can be used to successfully detect MRD.
Citation Format: Maysun M. Hasan, Juber Patel, Ian Johnson, Fanli Meng, Grittney K. Tam, Xiaohong Jing, Julie L. Yang, A. Rose Brannon, Jayakumaran Gowtham, Dennis P. Stephens, Monica Diosdado, Ryma Benayed, Ahmet Zehir, Chin-Tung Chen, Martin R. Weiser, Dana Tsui, Brian Houck-Loomis, Michael Berger. Tracking minimal residual disease in post-operative cell-free DNA using MSK-ACCESS [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 1387.