Gastric cancer with peritoneal metastases: Efficiency of standard treatment methods

Background: Peritoneal metastasis (PM), arising from gastric cancer (GC), is the most common pattern of synchronous and metachronous dissemination and is generally associated with poor prognosis. New therapeutic modalities are being increasingly employed for such patients.

Aim: To develop more advanced methods, it becomes necessary to study the results of existing standard treatment methods in patients with PM in order to perform a comparative analysis of the strategies.

Methods: A retrospective analysis of the efficiency of standard treatment methods (i.e., palliative chemotherapy, palliative gastrectomy, and the best supportive care) was performed on 200 GC patients with synchronous PM.

Results: The overall survival (OS) rate in 200 GC patients with PM under standard treatment was 5.4 mo. One-year survival occurred in 18.4% of patients. In multivariate analysis, the survival rate was significantly influenced by the following factors: Presence of extraperitoneal metastases, and stage of PM according to both the Japanese Gastric Cancer Association (JGCA) and the peritoneal cancer index (PCI). The median OS and 1-year survival of patients with Р1, P2, and P3 (JGCA) carcinomatosis were 9.8 mo, 6.7 mo, and 4.0 mo, and 47.2%, 18.8%, and 5.1%, respectively. The application of the palliative gastrectomy resulted in an increase in the median OS by up to 17 mo compared to the conservative approach where the value was 8.5 mo (P = 0.05) in patients with Р1 РМ. In patients with Р3, palliative chemotherapy increased the OS by up to 5.6 mo compared to the OS of 3.2 mo (P = 0.0006) for best supportive care. The median OS and 1-year survival of patients with РCI of 1-6, 7-12 and 13+ points were 8.5 mo, 4.2 mo, and 4.1 mo, and 39.8%, 6.7%, and 5.5%, respectively. Palliative gastrectomy increased the median OS to 12.6 mo compared to conservative approach of 8.0 mo (P = 0.03) in patients with РCI of 1-6 points. In patients with РCI 13+ points, only palliative chemotherapy increased the OS to 6.0 mo compared to the OS of 3.4 mo for best supportive care (P = 0.0008).

Conclusion: GC patients with PM are characterized by extremely poor prognoses. Long-term survivors were found in the group with PCI of 1-6 points, and there was no survival difference in groups with PCI 7-12 vs PCI 13+ points. Palliative gastrectomy could prove effective in treating patients with early stage PM. The three standard treatment methods are equally effective for moderate stages of PM. In cases with advanced peritoneal carcinomatosis, a significant increase in prognosis was registered only after treatment with palliative chemotherapy.