Decision-making of ctDNA in Patients With mCRC After Failure of First-line Treatment Containing Cetuximab - a Single-center, Phase II Clinical Study

After PD, patients received ctDNA testing, and different research protocols were selected according to different gene states of ctDNA, as follows: 1.No secondary changes related to drug resistance were found. Cetuximab cross-line + second-line chemotherapy (FOLFOX/FOLFIRI/ Irinotecan monotherapy, etc.) was used.2. If there is a RAS secondary mutation, change of beacizumab bead sheet resistance + second-line chemotherapy (FOLFOX/XELOX/stand for kang single-agent FOLFIRI mXEIRI/Iraq, etc.);3. If BRAF secondary mutation occurs, replace it with vimofenib + cetuximab + irinotecan;4. If HER2 amplification occurs, replace it with trastuzumab + lapatinib or trastuzumab + pertuzumab;5. In case of other secondary mutations, bevacizumab plus second-line chemotherapy should be replaced.