Conversion Surgery for Gastric Cancer with Peritoneal Metastasis Based on the Diagnosis of Second-Look Staging Laparoscopy

Background Patients with positive peritoneal cytology (CY1) or peritoneal dissemination (P1) have significantly poor prognosis. We performed pre-therapeutic staging laparoscopy (SL) to diagnose peritoneal metastasis for patients with advanced gastric cancer. When peritoneal metastasis disappears by chemotherapy for patients with CY1 or P1, we have intention to perform conversion surgery (CS). This study aims to clarify the clinical significance of CS for such patients. Methods We retrospectively analyzed clinical outcomes of 115 patients with advanced gastric cancer (large type 3, type 4, serosa-invasion) who underwent SL between 2005 and 2014. Disappearance of peritoneal metastasis was confirmed by second-look SL. Results CY0P0, CY1P0, and P1 were found in 56, 26, and 33 patients, respectively. In patients with CY1P0, 12 patients (66.7%) underwent CS (R0) as peritoneal cytology turned negative. All cases received S-1-based regimens, with median five treatment courses. The survival of patients with CS was significantly longer than those without CS (median survival time (MST); 41 vs. 11 months, respectively, P < 0.001). We observed no difference in overall survival between patients who underwent CS and patients with CY0P0 at the first SL (P = 0.913). All patients with P1 received chemotherapy. As peritoneal metastasis of five patients (15.2%) disappeared by chemotherapy, those patients underwent the CS (R0). The survival of patients who underwent CS was significantly longer than those who did not (MST; 31 vs. 10 months, respectively, P = 0.034). Conclusion This study suggests that conversion surgery contributes to improvement in survival of patients with peritoneal metastasis.