Prognostic Significance of Post-Neoadjuvant Chemotherapy Carbohydrate Antigen 19-9 Levels in Patients With Resectable Pancreatic Cancer Treated With S-1 and Gemcitabine: A Retrospective Cohort Study

Abstract

Purpose: Although carbohydrate antigen 19-9 (CA19-9) may exhibit low sensitivity in tumor screening, its prognostic significance has been highlighted. This study assessed the significance of preoperative CA19-9 and early postoperative CA19-9 levels in patients with nonmetastatic colorectal cancer (CRC).

Methods: Patients diagnosed with stage I-III CRC between January 2004 and April 2014 were included. Preoperative CA19-9 was assessed within 2 months of operation, whereas postoperative CA19-9 was measured 4 to 7 days after operation. The optimal cutoff values for preoperative and postoperative CA19-9 were established to maximize the differences in overall survival. Patients were categorized into 3 groups based on the CA19-9 change (CA19-9 trend): group 1, low preoperative CA19-9; group 2, high preoperative and low postoperative CA19-9; and group 3, high preoperative and postoperative CA19-9. The discriminatory powers of all variables were compared using the concordance index.

Results: A total of 816 patients were included. The determined cutoff values for preoperative and postoperative CA19-9 were 18.9 and 21.4 U/mL, respectively. Subgroup dichotomization revealed associations of preoperative CA19-9, postoperative CA19-9, and CA19-9 trend with overall survival in univariable analysis. The CA19-9 trend emerged as an independent prognostic factor in the multivariable analysis (group 1 vs. group 2: hazard ratio, 1.682 [95% confidence interval (CI), 1.043-2.710], P=0.032; group 1 vs. group 3: hazard ratio, 2.882 [95% CI, 1.899-4.371], P<0.001). The concordance index value of the CA19-9 trend (0.636; 95% CI, 0.509-0.682) surpassed those of preoperative and postoperative CA19-9.

Conclusion: The amalgamation of preoperative and postoperative CA19-9 levels demonstrated enhanced prognostic stratification, allowing for a more detailed classification of patients with nonmetastatic CRC.