Purpose: Although carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9 are the most commonly used tumor markers in gastric cancer, the differences in the characteristics of these two markers remain unclear, because most previous studies have included many patients who were positive for both markers. Methods: We analyzed the available data on 1050 patients with gastric cancer who underwent R0 resection. The background characteristics and recurrence-free survivals (RFS) were compared between the single-positive patients for CEA or CA 19-9 and double-negative patients. Results: Among these 1050 patients, 86 patients (8.2 %) were positive for CEA only, 77 patients (7.3 %) were positive for CA 19-9 only, and 867 patients (82.6 %) were double negative for both markers. Patients who were elderly, male and had a differentiated histology were more commonly observed in the CEA-positive group than in the double-negative group (P = 0.004, P = 0.009, and P = 0.001). The patients who were positive for either CEA or CA 19-9 had a significantly worse RFS than the patients who were negative for both (P < 0.001 and P < 0.001). The most frequent site of recurrence was the liver (9.3 %) in the CEA-positive group and the peritoneum (11.7 %) in the CA 19-9-positive group. Conclusion: Age, sex, and histological type were thus found to be associated with CEA positivity. CEA is, therefore, considered to be a sensitive marker for liver recurrence, while CA 19-9 is a sensitive marker for peritoneal recurrence.
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