Value of Carcinoembryonic Antigen Levels After Chemoradiotherapy for Advanced Low Rectal Cancer

Background/Aim: Preoperative chemoradiotherapy (CRT) followed by total mesorectal excision is the standard treatment for advanced low rectal cancer; however, long-term oncological outcomes vary widely, and reliable prognostic biomarkers remain limited. Carcinoembryonic antigen (CEA) is commonly used in colorectal cancer management, but the prognostic value of post-CRT CEA levels has not been fully clarified. This study aimed to identify clinically relevant prognostic factors for recurrence and survival, with particular focus on pre- and post-CRT CEA levels. Patients and Methods: A retrospective review was conducted of 41 consecutive patients with advanced low rectal cancer (Rb, cT3/4 or N1/2 and no lateral lymph node metastasis) who underwent long-course preoperative CRT followed by radical surgery. CRT consisted of 45 Gy in 25 fractions with concurrent tegafur/uracil, followed by total mesorectal excision 8-10 weeks after CRT completion. Clinicopathological factors were analyzed in relation to recurrence, disease-free survival (DFS), and overall survival (OS). Results: With a median follow-up of 69.3 months, recurrence occurred in 16 patients. Five-year DFS and OS rates were 59.4% and 73.2%, respectively. Univariate analysis identified postoperative complications, pathological complete response, and pre- and post-CRT CEA levels as significant factors associated with recurrence. Multivariate analysis demonstrated that post-CRT CEA was the only independent prognostic factor. Receiver operating characteristic analysis identified a post-CRT CEA cut-off value of 3.9 ng/ml. Patients with lower post-CRT CEA showed significantly better DFS and OS. Conclusion: Post-CRT CEA is a valuable prognostic biomarker for recurrence and survival in advanced low rectal cancer, and patients with elevated post-CRT CEA may benefit from additional consolidation chemotherapy.