Additionally, a decline in serum CEA levels was observed in most patients, even during long-term follow-up.22 In a related preclinical study, the intraperitoneal (IP) administration of CEA-targeted CAR-T cells was investigated for treating peritoneal carcinomatosis originating from CRC.37 The study involved 24 mice, divided into three groups of 8: a control group, a group receiving intravenous (IV) CAR-T cell administration, and a group receiving IP CAR-T cell administration. Here, CEACAM5 is linked to colorectal carcinoma.