Background: Most colorectal cancer (CRC) deaths are caused by metastatic disease (mCRC). Therapeutic approaches include treatment with monoclonal antibodies (mAbs) against EGFR and VEGF. There is an urgent clinical need to stratify mCRC patients for optimal treatment. Cell-free circulating tumor DNA (ctDNA) derived from blood plasma is expected to improve stratification by early detection of therapy resistance and disease progression.

Aim: The general aim of this study is to advance towards clinical implementation of ctDNA-based tests as molecular biomarkers to improve disease management of mCRC patients. We will investigate added value of liquid biopsy ctDNA-based gene mutation analyses compared to: 1) tissue-based tests for RAS mutation status as determined in standard clinical care setting; and 2) monitoring of disease progression by computed tomography (CT) imaging.

Methods: CAIRO5 is a multicenter, randomized, phase 3 clinical trial of the Dutch Colorectal Cancer Group (DCCG) and includes patients with initially unresectable, liver-only mCRC, as confirmed by a central panel of liver surgeons/radiologists based on CT imaging. This study involves nation-wide longitudinal collection of liquid biopsies (blood samples) using cell-save tubes and CT imaging from up to 564 patients. Hotspot mutations in ctDNA will be analyzed by droplet digital PCR (ddPCR), and mutations in a panel of genes by targeted error correction sequencing (TEC-seq). Clinical, imaging, biobanking, and molecular data will be collected using standardized data fields and data formats and integrated for querying and viewing in tranSMART, making use of the national Health-RI research IT infrastructure.

Results: The nation-wide multi-center logistics for longitudinal blood sample collection and plasma processing has been established, with participation of more than 40 Dutch hospitals. At present (Nov 2017), over 220 patients have been included from whom more than 550 blood samples and 330 CT images were obtained. Proof of concept for the validity of this workflow was obtained by successful subjection of 11 plasma samples to ctDNA mutation analysis by TEC-seq (Phallen et al., 2017).

Discussion: Implementation of ctDNA-based tests as molecular biomarkers to improve disease management of mCRC patients requires collection of information from large, well-defined studies with longitudinal patient follow-up. This translational research project will provide the data that are needed to determine cost-effectiveness analysis of ctDNA mutation analyses by health technology assessment, yielding recommendations for clinical implementation of ctDNA applications.

Citation Format: Iris van 't Erve, Jillian Phallen, Karen Bolhuis, Joost Huiskens, Nicole C. van Grieken, Veerle Coupé, Annegien Broeks, Daan van den Broek, Alessandro Leal, Victor E. Velculescu, Cornelis J. Punt, Gerrit A. Meijer, Remond J. Fijneman. Liquid biopsy analyses of cell-free circulating tumor DNA as predictive and prognostic biomarker for colorectal cancer patients with metastatic disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1588.