Risk Factors for Peritoneal Recurrence in Stage II/III Gastric Cancer Patients Who Received S-1 Adjuvant Chemotherapy After D2 Gastrectomy

The peritoneum is still the most frequent site of recurrence in stage II/III gastric cancer patients, although the survival rate was improved by the introduction of S-1 adjuvant chemotherapy. The objective of this retrospective study was to clarify the risk factors for peritoneal recurrence in patients who received S-1 adjuvant chemotherapy. Peritoneal recurrence-free survival was examined in 100 gastric cancer patients who underwent curative D2 surgery, which were diagnosed with stage II or III disease pathologically, and received adjuvant S-1 between June 2002 and March 2011. The univariate and multivariate analyses were performed to identify risk factors by a Cox proportional hazards analysis. The P-RFS was 64.3% at 3 years and 58.8% at 5 years. A total of 18 patients were diagnosed with peritoneal recurrence. The macroscopic tumor diameter, depth of tumor invasion, and lymph node metastasis were the significant factors identified by the univariate analysis, while the tumor diameter and lymph node metastasis were the only significant independent risk factors identified by the multivariate analysis. The macroscopic tumor diameter and presence of lymph node metastasis were the most important risk factors for peritoneal recurrence. When patients had these risk factors, S-1 was not sufficient to inhibit peritoneal recurrence. A novel adjuvant chemotherapeutic agent targeting peritoneal metastasis in these patients should be developed.