Adjuvant Chemotherapy with S-1 Followed by Docetaxel for Gastric Cancer and CY1P0 Peritoneal Metastasis after Relatively Curative Surgery

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Objective: The aim of this study was to assess the feasibility and safety of adjuvant chemotherapy with S-1 followed by docetaxel.
Patients and Method: Twenty-eight patients with advanced gastric cancer underwent gastrectomy without preoperative chemotherapy. These patients were divided into 3 groups on the basis of cytologic results of peritoneal lavage (CY) and the presence of local peritoneal metastatic nodules (P): CY1-P0, CY0-P1, and CY1-P1. Oral S-1 (80 mg/m²/day) was administered for 3 consecutive weeks, followed by intravenous docetaxel (35 mg/m²) on days 29 and 43 (1 cycle). This cycle was repeated every 8 weeks. The primary endpoint was the ability to complete 6 cycles of S-1 followed by docetaxel. The secondary endpoints were safety, progression-free survival, mean survival time (MST), and overall survival (OS).
Results: The subjects were 18 men and 10 women (39 to 78 years old, median age, 64 years). The extent of peritoneal metastasis was CY1-P0 in 8 patients, CY0-P1 in 14 patients, and CY1-P1 in 6 patients. Both hematologic and nonhematologic toxicities were generally mild. The completion rate of the planned 6 cycles of the protocol was 71.4% (20 of 28 patients). Median progression-free survival was 22.9 months, and the 2-year survival rate was 78.6%. The overall MST was 34.3 months, and the MST by group was 34.5 for CY1-P0, 34.3 for CY0-P1, and 19.3 months for CY1-P1. The OS in the CY1-P0 and CY0-P1 groups was significantly longer than that in the CY1-P1 group (P<0.05).
Conclusion: Adjuvant chemotherapy with S-1 followed by docetaxel is safe and well tolerated and has the potential to improve OS in patients with a status of CY1P0 following relatively curative resection.