De-scalation or swItch of Treatment According to Circulating tuMOr DNA Variation After 2 Cycles of Doublet Chemotherapy Plus Targeted Agent in Metastatic Unresectable Colorectal Cancer

"after 4 cycles of doublet + TA, non-progressive patients will be allocated to a strategy according to ctDNA value and variation from C1-C3: Arm A1: CT discontinuation (ctDNA normalization \< 0.1 ng/ml or ctDNA not detectable) Arm A2 : maintenance with fluoropyrimidine + TA (ctDNA ≥ 0.1 ng/ml and ∆ctDNA≥ 80%).~Arm A3 : ctDNA non-responders (∆ctDNA \< 80% or increase) : switch of CT +/- TA."

At least 8 cycles of doublet CT + TA before adaptation of sequence at physician choice.