In multivariable analysis, an unfavourable IgG trajectory independently predicted recurrence or death (HR 2.05, 95% CI 1.32-3.18), whereas CEA trajectory was not significant.<h4>Conclusion</h4>Dynamic postoperative IgG monitoring is independently associated with disease recurrence in high-risk stage II-III colorectal cancer and offers incremental prognostic value beyond CEA. The gene discussed is CEACAM5; the disease is colorectal cancer.