Efficacy of adjuvant chemotherapy with S-1 in patients with positive peritoneal cytology (CY1) who underwent R1 surgery.
84 Background: In recent TNM classification, positive peritoneal cytology (CY1) is regarded as M1 disease and classified into stage IV. However, the prognosis of the CY1 patients underwent R1 surgery (microscopic residual tumor) is considered to be relatively better than those underwent R2 surgery (macroscopic residual tumor). Adjuvant chemotherapy with S-1 had demonstrated significant survival benefit in stage II and III gastric cancer in Japan. However, the efficacy of adjuvant S-1 in patients with relatively more advanced stage had not been investigated. Therefore, we investigated the efficacy of adjuvant chemotherapy with S-1 in CY1 patients underwent R1 surgery. Methods: Among the 2,202 patients with gastric cancer treated at our department between September 2002 and July 2009, a total of 105 patients with CY1 and underwent R1 surgery were included in this study. Clinocopathological features and survival were retrospectively analyzed using prospectively registered data base system. Results: There were 64 male and 41 female patients. The median age was 61 years old. Eighty-five patients had T4a or T4b tumor and 96 patients had lymph node metastasis. Seventy-eight patients had undifferentiated type of tumor. In 83 patients, adjuvant chemotherapy with S-1 had been performed. In the uni-variate analysis, only the extent of lymph node dissection (D2) and the adjuvant chemotherapy with S-1 demonstrated significant survival benefit. In multi-variable analysis using Cox proportional hazarded model, N-factor, extent of lymph node dissection (D2 vs D1), and adjuvant chemotherapy with S-1 were selected as independent prognostic factors. The median survival time and 5-year survival rate in patients underwent R1 resection with D2 lymphadenectomy and adjuvant S-1 treatment were 42 months and 46%, respectively. Conclusions: In patients with CY1 and underwent R1 surgery, adjuvant chemotherapy with S-1 demonstrated significant survival benefit. In patients with positive peritoneal cytology without other non-curative factors, D2 lymph node dissection and adjuvant chemotherapy using S-1 is recommended. No significant financial relationships to disclose.