Advances in Intraperitoneal Chemotherapy for Gastric Cancer Patients with Peritoneal Metastases: Current Status of Treatment and Institutional Insights.

Introduction: Peritoneal metastasis (PM) is the most common site of recurrence following curative resection for advanced gastric cancer (GC). Along with disease progression, it can lead to complications such as intestinal obstruction, hydronephrosis, obstructive jaundice, and ascites, significantly impairing the patient's quality of life. Therefore, peritoneal metastasis is considered a critical target for treatment. In general, these patients are treated with systemic chemotherapy; however, the therapeutic effect is often limited due to the anticancer agents' poor penetration into the peritoneal cavity. We aim to identify factors associated with the best overall survival (OS) in GC patients with peritoneal metastasis. Methods: Patients with advanced GC who were diagnosed as having macroscopic PM or positive peritoneal cytology by staging laparoscopy were enrolled. We introduced intraperitoneal Paclitaxel (IP-PTX) combined with S-1 plus oxaliplatin (SOX). Gastrectomy with lymph node dissection was performed as conversion surgery when the PM showed an excellent response. Results: Ninety-six patients received IP-PTX + SOX, with a median of 16 courses. The 1- and 5-year OS rates were 70.2% and 24.5%, respectively, with a mean survival time (MST) of 20.0 months. No chemotherapy-related mortality was observed. Conversion surgery was performed in 44 patients (45.8%), with a 1-year OS rate of 100%. Conclusions: Combination chemotherapy using the IP-PTX + SOX regimen is highly effective and is recommended as induction chemotherapy for patients with PM from GC. Conversion gastrectomy should be considered following an excellent response, particularly in patients with peritoneal cancer index (PCI) scores below 20.