Pressurized intraperitoneal aerosol chemotherapy (PIPAC) for unresectable PM from gastric cancer outstanding result from multicenter cohort study

331 Background: PIPAC is a recent approach for intraperitoneal chemotherapy with promising results for patients with peritoneal metastasis (PM). It is a safe and well-tolerated treatment. Our aim was to report oncological outcomes after PIPAC for gastric PM. Methods: International retrospective cohort study of consecutive patients with gastric PM. Outcome measures were overall survival (OS), radiological response (RECIST), histological response by use of Peritoneal regression grading system (PRGS) and cytology, peritoneal cancer index (PCI) and symptoms. Results: 586 non-selected patients with a median age of 56 (47-64) years, 54% of them were female and underwent a total of 1566 PIPAC procedures. 37% of patients were treated with 2 or more lines of IV chemotherapy, median PCI at first PIPAC was 14 (7-24) and 63% of them were with signet ring adenocarcinoma. Grade III-IV morbidity was 5.1 % and 1.9% died within 30 days from PIPAC procedure. Median OS was 15.4 months from diagnosis and 20.1 months for patient with more than 3 PIPAC. 263/586 patients (44.9%) had ≥3 procedures ( pp: per protocol) with the following outcomes: RECIST: 4.3% complete response 11% partial remission, 44% stable; PRGS1 39% at PIPAC3 and negative cytology at PIPAC3 in 16% of patient. In multivariate analysis, 3 PIPAC or more HR 0.3 (95% CI 0.27-0.51), 2nd and 3rd line of chemotherapy HR 0.48 (95% CI 0.25-0.92) and CRS&HIPEC after PIPAC HR 0.3 (95% CI 0.18-0.51) were predictors for survival. Conclusions: Based on this large multicentre cohort study, PIPAC could be considered as an option for the treatment of PM from gastric cancer. More prospective study will validate this indication in the near future.