CEACAM5 and rectal cancer: Multivariate Cox analysis demonstrated that ACT tended to be a protective factor in ypT3N0M0 rectal cancer patients with elevated pretreatment serum CEA levels (HR = 0.633, 95% CI = 0.344–1.164, P = 0.141), while ACT was not associated with improved CSS in ypT3N0M0 rectal cancer patients with normal pretreatment serum CEA levels (HR = 1.035, 95% CI = 0.487–2.202, P = 0.928).