Static carcinoembryonic antigen (CEA) levels are well‑established prognostic markers in patients with gastric cancer, but the significance of their dynamic trajectories over time has rarely been reported.

We analysed the perioperative CEA levels (presurgery, early postsurgery, and late postsurgery) of 578 gastric cancer patients who underwent curative resection, with a median follow-up of 29 months. We used the entire cohort for k-means clustering. Survival differences between clusters were assessed using Kaplan–Meier analysis and Cox regression.

Of the 578 patients, 15.57% exhibited elevated CEA levels before surgery (median 2.07 ng/mL), which then decreased to 3.29% (median 1.74 ng/mL) after surgery. However, after six months, a slight rebound was observed (18.51% elevated, median 2.98 ng/mL). K-means clustering identified three CEA trajectories: high, medium, and low (Calinski–Harabasz index: 358). Survival analysis demonstrated that higher CEA trajectories were associated with worse disease-free survival (DFS) and overall survival (OS). With the low cluster as a reference, multivariate Cox regression analysis revealed that a higher CEA trajectory was an independent prognostic factor, with an elevated risk in the high cluster (HR 2.64, 95% CI: 1.37-5.0), indicating that the high cluster had more than twice the mortality risk of the low cluster and that the medium cluster had a moderately increased mortality risk (HR 1.69, 95% CI: 1.0-2.85).

Higher CEA trajectories are associated with a worse prognosis, highlighting the importance of enhanced monitoring for this group of patients.