本研究的目的是调查胃癌同步或异时腹膜转移 (PM) 的发病率、危险因素和治疗，并使用基于人群的数据估计这些患者的生存率。 2015年至2016年诊断出胃癌的患者选自荷兰癌症登记处。计算同步和异时 PM 的发生率。进行多变量回归分析以确定与 PM 发生相关的因素。比较同步性和异时性 PM 患者的治疗和生存率。在 2206 名胃癌患者中，741 名（34%）被诊断为 PM。其中，498 人 (23%) 有同步 PM。接受潜在治愈性治疗的患者 (n=675) 3 年时异时性 PM 的累积发生率为 22.8%。与同步和异时性 PM 相关的一个因素是弥漫型组织学。诊断为同步性 PM 的患者比异时性 PM 患者更常接受全身治疗（分别为 35% 和 18%，P < .001）。同步和异时 PM 之间的中位总生存期相当（分别为 3.2 个月和 2.3 个月，P = .731）。大约三分之一的胃癌患者在初次诊断时或在潜在治愈性治疗后的 3 年随访期间被诊断为 PM。与同步性 PM 患者相比，异时性 PM 患者较少接受全身治疗，但两组之间的生存率相当。未来的试验有必要在早期阶段检测出胃癌，并研究降低腹膜传播风险的策略。此外，还应进一步研究胃部 PM 患者的具体治疗方案。© 2023 UICC。

The aims of this study were to investigate incidence, risk factors and treatment of synchronous or metachronous peritoneal metastases (PM) from gastric cancer and to estimate survival of these patients using population-based data. Patients diagnosed with gastric cancer in 2015 to 2016 were selected from the Netherlands Cancer Registry. The incidence of synchronous and metachronous PM were calculated. Multivariable regression analyses were performed to identify factors associated with the occurrence of PM. Treatment and survival were compared between patients with synchronous and metachronous PM. Of 2206 patients with gastric cancer, 741 (34%) were diagnosed with PM. Of these, 498 (23%) had synchronous PM. The cumulative incidence of metachronous PM in patients who underwent potentially curative treatment (n = 675) was 22.8% at 3 years. A factor associated with synchronous and metachronous PM was diffuse type histology. Patients diagnosed with synchronous PM more often received systemic treatment than patients with metachronous PM (35% vs 18%, respectively, P < .001). Median overall survival was comparable between synchronous and metachronous PM (3.2 vs 2.3 months, respectively, P = .731). Approximately one third of all patients with gastric cancer are diagnosed with PM, either at primary diagnosis or during 3-year follow-up after potentially curative treatment. Patients with metachronous PM less often received systemic treatment than those with synchronous PM but survival was comparable between both groups. Future trials are warranted to detect gastric cancer at an earlier stage and to examine strategies that lower the risk of peritoneal dissemination. Also, specific treatment options for patients with gastric PM should be further investigated.© 2023 UICC.