Conversion surgery for advancedgastric cancer with peritoneal metastasis.

Abstract

450 Background: Patients with peritoneal metastasis have significantly poor prognosis. We have performed pretherapeutic staging laparoscopy (SL) to diagnose peritoneal metastasis for patients with large type 3, type 4 or serosa-invasive gastric cancer. When peritoneal metastasis disappears by chemotherapy for patients with positive peritoneal cytology (CY1) or peritoneal dissemination (P1), we perform the conversion surgery (CS). Methods: We retrospectively analyzed clinical outcomes of 134 patients with advanced gastric cancer who underwent SL between 2005 from 2016. We examined safety and usefulness of CS for patients with CY1 or P1. Results: CY0P0, CY1P0 and P1 were found in 67, 28 and 39 patients, respectively. The median survival time (MST) of patients with CY0P0, CY1P0 and P1 were 39, 21 and 11 months (CY0P0 vs CY1P0; p = 0.029, CY0P0 vs P1; p<0.001, CY1P0 vs P1; p<0.001). In patients with CY1P0, 20 of 26 patients who received chemotherapy underwent the second look SL, and 14 patients (54%) underwent CS (R0) as peritoneal cytology turned negative. These regimens of chemotherapy were S-1/CDDP (n = 9), Docetaxel/CDDP/S-1 (n = 2), SOX (n = 2) and S-1/Docetaxel (n = 1) and the median number of treatment courses was5courses. The MSTs of patients with or without CS were 40 months and 11 months (p<0.001). Then, there was no difference in overall survival between patients with CS and patients with CY0P0 at the first SL (p = 0.866). All patients with P1received chemotherapy, and 11 of these patients underwent the second look SL. As peritoneal metastasis of 7 patients (18%) disappeared by chemotherapy, they underwent CS (R0). The MSTs of patients with or without CS were 31 months and 9 months (p = 0.026). Regarding complications after CS, surgical-site infection and interstitial pneumonia each occurred in one patient (grade II), and intestinal obstruction (grade IIIa) occurred in one patient. There was no mortality. Conclusions: This study suggests that CS is probably safe and may contribute to improve the survival rate of patients with peritoneal metastasis. Moreover, we developed the NSOX regimen, comprised of a combination nab-paclitaxel, S-1 and oxaliplatin, and have performed a phase I/II trial using the NSOX regimen (UMIN000030909).