The exploration of surgery and survival prediction in patients with peritoneal metastasis from gastric adenocarcinoma based on the SEER database.

Background: As one of the most common diseases in terms of cancer-related mortality worldwide, gastric adenocarcinoma (GA) frequently develops peritoneal metastases (PMs) in advanced stages. Systemic therapy or optimal supportive care are recommended for advanced GA; however, patients frequently develop drug resistance. Surgical resection is not recommended for stage IV patients, and there have been some controversies regarding the role of it in GA patients with PMs. The aim of the study was to preliminarily evaluate the possible effect of surgical treatments on patients with only PMs from GA. Methods: Data were collected from the Surveillance, Epidemiology and End Results (SEER) database (year 2000-2022). A propensity score matching (PSM) was performed to reduce the influence of selection bias and confounding variables on comparisons. Then Cox proportional hazard regression, Kaplan-Meier analysis, and log-rank test were performed to assess the efficacy of surgical treatment in patients with PMs from GA. Results: A total of 399 patients diagnosed with PMs from GA were enrolled for our analysis, of which, 180 (45.1%) patients did not receive surgery and 219 (54.9%) patients received surgery. Multivariate Cox regression analysis before PSM indicated higher rates of overall survival (OS) outcome for patients who had received surgery [hazard ratio (HR) =0.4342, 95% confidence interval (CI): 0.3283-0.5742, P<0.001]. After PSM, a total of 172 patients were enrolled, with 86 in each group. Multivariate Cox analysis showed that surgery was the independent factor reflecting patients' survival (HR =0.4382, 95% CI: 0.3037-0.6324, P<0.001). Subgroup survival analysis revealed that surgery may bring advantages to patients with grades I-IV, stages T1-T4, stage N0, and tumor size less than 71 mm (P<0.05). We also found that the OS of chemotherapy patients who had undergone surgery was better than that of chemotherapy patients who had not undergone surgery (P<0.01). Conclusions: Based on the SEER database, surgery has better OS for patients only with PMs from GA. Patients without lymph node metastasis and those who received chemotherapy before may benefit from surgery. These specific groups of patients may have surgery as an option to improve the prognosis.