Piers Robert Bristow Boshier, Daryl K A Chia, Sri G. Thrumurthy, Jun Liang Teh, Maria Wobith, Maria Bencivenga, Federica Filippini, Teodora Dumitra, Miguel Burch, Hyoung-il Kim, Benjamin Kobitzsch, Liudmila L. Kodach, Judith S. E. Quik, Vo Duy Long, Micha J. de Neijs, P. van der Sluis, Alberto M. León-Takahashi, Yanghee Woo, Mickaël Chevallay, Massimo Framarini, P. Morgagni, Ewelina Frejlich, Heike I. Grabsch, Sheraz R Markar, Daniele Marrelli, Do Joong Park, Raghav Sundar, Zekuan Xu, Kay Khine Linn, Han Kwang Yang, Joji Kitayama, Z. A. Zhu, Sun Young Rha, Bas Wijnhoven, Hiroharu Yamashita, Wei Peng Yong, C. de la Fouchardière, Marie Nilsson, Hironori Ishigami, Johanna W Van Sandick, F. Lordick, Brian D Badgwell, Jimmy Bok-Yan So
BACKGROUND: Gastric cancer peritoneal metastasis (GCPM) is a common manifestation of advanced gastric cancer, associated with poor prognosis. METHODS: The International Gastric Cancer Association (IGCA) convened a multidisciplinary working group of 42 global experts from 15 countries to develop a total of 13 consensus statements addressing diagnosis, treatment, and research priorities for GCPM. Using ACcurate COnsensus Reporting Document (ACCORD)-compliant methodology, the group conducted systematic literature searches and applied a structured Delphi process with anonymous Likert-scale voting and a ≥70% consensus threshold to generate and refine consensus statements. RESULTS: Consensus was achieved for all 13 statements among the working group during the first Delphi round, with 75-100% of respondents selecting either 'strongly agree' or 'agree'. Coefficient of variation values were ≤0.23. Polling of a broader group of experts (n = 66), which included members of the working group (n = 21), during a GCPM consensus session at the 16th International Gastric Cancer Congress (IGCC) in 2025 demonstrated agreement for 12 of the 13 statements. This broader group of experts, which had greater representation from medical oncologists, did not reach consensus (52% agreement) on best practice for systemic treatment of patients with GCPM, possibly due to the rapidly evolving developments in this field of metastatic gastric cancer. CONCLUSION: This consensus exercise provides a foundation for globally relevant GCPM management strategies and highlights critical research needed to address significant evidence gaps that will improve patient outcomes.