CEACAM5 and Oral ulcer: CKI also improved the objective response rate (ORR, RR = 1.50, 95% CI: 1.38 to 1.62, p < 0.00001) and disease control rate (DCR, RR = 1.15, 95% CI: 1.10 to 1.19, p < 0.00001), decreased CEA levels (MD = −1.79, 95% CI: −2.81 to −0.76, p = 0.0007) and CA199 levels (MD = −0.73, 95% CI: −1.35 to −0.12, p = 0.02), and reduced chemotherapy-induced adverse reactions, including nausea, vomiting, hepatic dysfunction, myelosuppression, neurotoxicity, leukopenia, thrombocytopenia, and mouth ulcers.