If the carcinoembryonic antigen is found to be elevated after chemotherapy, the first step should be to conduct relevant imaging review to evaluate the efficacy of chemotherapy. If the carcinoembryonic antigen is elevated and the imaging results also indicate the progression of the lesion, it means that the original chemotherapy regimen is ineffective, the lesion is uncontrolled, and the disease is progressing, so it is necessary to adjust the chemotherapy regimen or change other treatment methods. If only the carcinoembryonic antigen is elevated and the imaging indicates stable lesion, it is possible that the tumor tissue necrosis and disintegration after chemotherapy may cause temporary elevation of carcinoembryonic antigen, and the original chemotherapy regimen can be continued. Therefore, if carcinoembryonic antigen is elevated after chemotherapy, we should analyze the reasons and evaluate the efficacy of chemotherapy in combination with imaging results to decide whether to change the chemotherapy regimen or change the treatment method.