662P - Gastrectomy after response to intraperitoneal and systemic chemotherapy for gastric cancer with peritoneal metastasis or positive peritoneal cytology

Abstract

Background: The prognosis of gastric cancer patients with peritoneal metastasis (P1) or positive peritoneal cytology (CY1) remains poor in spite of recent progress in systemic chemotherapy. We developed several regimens combining intraperitoneal (IP) and systemic chemotherapy, and evaluated the safety and efficacy in clinical trials. Gastrectomy after response to combination chemotherapy is a promising option for P1 or CY1 gastric cancer. A retrospective study was performed to evaluate this multidisciplinary treatment strategy. Methods: This study enrolled 158 primary P1 or CY1 gastric cancer patients treated with IP paclitaxel or docetaxel with systemic chemotherapy at the University of Tokyo Hospital between 2005 and 2015. Gastrectomy was performed when peritoneal cytology turned negative, and the disappearance or obvious shrinkage of peritoneal metastasis was confirmed by laparoscopy. Combination chemotherapy was restarted after surgery and repeated with appropriate dose reduction. Results: Ninety-one patients were chemo-naïve, and 67 patients had received standard systemic chemotherapy at the previous hospitals before the initiation of IP chemotherapy. Gastrectomy was performed in 94 (P1 85, P0CY1 9) of 158 (P1 147, P0CY1 11) patients after response to chemotherapy. R0 resection was achieved in 61 of 94 patients (65%). Postoperative complications included anastomotic leakage in 3 patients and pancreatic fistula in 2 patients, which were cured conservatively. The median survival time (MST) of 94 patients with gastrectomy was 31.3 months (95% confidence interval [CI] 26.1-39.3 months) from the initiation of IP chemotherapy and 35.8 months (95% CI 28.5-40.1 months) from the diagnosis of gastric cancer. Relapse or progression was observed in 78 of 94 patients with a median time of 17.9 months (95% CI 15.0-24.2 months). The first site of recurrence or progression was the peritoneum in 61 patients and the other site in 28 patients (both in 11 patients). The MST of 64 patients without gastrectomy was 12.3 months (95% CI 10.0-13.9 months). Conclusions: Gastrectomy after response to intraperitoneal and systemic chemotherapy is safe and may prolong the survival of P1 and CY1 gastric cancer patients. Legal entity responsible for the study: The University of Tokyo Funding: Japan Agency for Medical Research and Development Disclosure: All authors have declared no conflicts of interest.