A Study of On-treatment ctDNA Changes in Chemo-refractory Colorectal Cancer Patients

COPERNIC is an international, multicentre, single-arm study. Chemo-refractory mCRC subjects who meet all eligibility criteria will be treated with standard systemic chemotherapy (the decision about the treatment regimen being made by the treating physician) and undergo tumour assessment by standard imaging (either CT scan or MRI scan) at baseline and every 8 or 12 weeks until evidence of tumour progression. Response to treatment will be assessed by the local investigators according to the RECIST criteria version 1.1. Blinded, independent central review of the imaging scan will be carried out, this having no impact on treatment decisions which will remain the prerogative of the treating physician. Serial blood samples from study subjects will be collected at pre-defined time points for ctDNA testing. Also, archived tumour tissue from each subject will be collected. Prospective and retrospective ctDNA analyses on blood samples will be carried out, and dynamics of ctDNA will be correlated with prognosis. Two ctDNA assays will be used in this study: * FoundationOne Liquid CDx (F1LCDx) for comprehensive genomic profile (CGP) assessment * F1Monitor for monitoring purpose For subjects receiving treatments with a 2- or 4-weekly schedule, blood and plasma samples for ctDNA testing will be collected at the following timepoints: Blood : * Before treatment start (day 1) * 2 weeks after treatment start (day 15) Plasma : * Before the treatment start (day 1) * 4 weeks after treatment start (day 29) * 8 or 12 weeks after treatment start and every 8 or 12 weeks thereafter (i.e. at the same time of each imaging tumour assessment) until evidence of progressive disease by RECIST 1.1 For subjects receiving treatments with a 3-weekly schedule, blood and plasma samples for ctDNA testing will be collected at the following timepoints: Blood : * Before treatment start (day 1) * 3 weeks after treatment start (day 22) Plasma : * Before treatment start (day 1) * 6 weeks after treatment start (day 43) * 8 or 12 weeks after treatment start and every 8 or 12 weeks thereafter (i.e. at the same time of each imaging tumour assessment) until evidence of progressive disease by RECIST 1.1 ctDNA analyses will be done in a centralised laboratory (Foundation Medicine Inc). Full report of the ctDNA analysis will be provided to the study team to allow correlation with clinical data and exploratory analyses. The results of the ctDNA analysis will not be communicated to the treating physician (with the only exception of the analysis by F1CDx on tumour tissue at screening) and therefore will not have any impact on treatment decision (i.e., all study subjects will be treated according to standard practice).