Abstract A35: Cell-free tumor DNA profiling of colon cancer patients: Searching for mechanisms of chemoresistance

Abstract

Abstract Colorectal cancer (CRC) is a worldwide health burden, with nearly 1.2 million new cases expected each year. Significant efforts are currently being employed to find patients who will benefit from chemotherapy. In fact, drug resistance is a limiting factor for the efficacy of chemotherapy in CRC treatment. In the present work, we aimed at identifying molecular markers in plasma cell-free DNA that could be associated with good/poor response and chemoresistance, comparing good responders (i.e., benefitting from chemotherapy, not having side effects like toxicity, no relapses, and having a complete response with no residual cancer) from non-/poor responders (patients with chemoresistance and lacking any response, or developing toxicity). Paired plasma samples from 10 colon cancer patients collected before and after adjuvant 5-fluorouracil (5-FU)-based therapy were profiled by a whole-exome sequencing (WES) approach in order to identify mutations associated with therapy response. In concomitance, DNA from tumor tissue from the same patients was also profiled by WES for mutation burden concordance. Analyses were performed on colon cancer patients treated with the same 5-FU-based therapy. The first sampling was performed at the time of the diagnosis (i.e., active disease), and the second after 6-9 months depending on patients’ conditions (i.e., covering the tumor resection, administration of adjuvant chemotherapy, etc.). After follow-up, 3 patients were clinically classified as “good responders” and 7 as “non-/poor responders.” All prepared libraries passed the quality control checkpoints and were sequenced. The number of total reads exceeds 2,57 × 109. Mean read length is about 100 nt. Alignment to human reference genome (hg38) is > 99.8%. The bioinformatics analyses are currently ongoing to profile the two different groups over time. Detailed results of the study will be presented during the meeting. The significance of the project lies in the improvement of the diagnosis and therapy efficacy in colon cancer patients. Supported by grant AZV MZ 17-30920A. Citation Format: Veronika Vymetalkova, Barbara Pardini, Marketa Urbanova, Klara Cervena, Pavel Vodicka, Alessio Naccarati. Cell-free tumor DNA profiling of colon cancer patients: Searching for mechanisms of chemoresistance [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr A35.