Gastric Cancer (GC) with Peritoneal Metastases (PMs): An Overview of Italian PSM Oncoteam Evidence and Study Purposes

SIMPLE SUMMARY: Peritoneal metastases (PMs), arising from gastric cancer (GC), are one of the most common patterns of synchronous and metachronous dissemination and are generally associated with a poor prognosis. New therapeutic modalities are being increasingly employed for such patients. Here, we provide an overview of the recent literature on this topic, along with two studies currently underway: one at Sapienza University of Rome and the other at the University of Verona, focusing on the use of neoadjuvant intraperitoneal chemotherapy in combination with a classical neoadjuvant systemic chemotherapy (SC). This overview emphasizes the results obtained using neoadjuvant intraperitoneal treatment, which may find a place not only in the Eastern world, where it now represents a standard of care, but also among Western practitioners. ABSTRACT: Gastric cancer (GC) continues to be one of the leading types of malignancies worldwide, despite an ongoing decrease in incidence. It is the fifth most frequent type of cancer in the world and the fourth leading cause of cancer death. Peritoneal metastases (PMs) occur in 20–30% of cases during the natural history of the disease. Systemic chemotherapy (SC) is undoubtedly the standard of care for patients with GC and PMs. However, with the development of highly effective regimens (SC combined with intraperitoneal chemotherapy), significant tumor shrinkage has been observed in many patients with synchronous GC and PMs, allowing some to undergo curative resection “conversion surgery” with long-term survival. In recent years, there has been growing interest in intraperitoneal chemotherapy for PMs, because the reduced drug clearance associated with the peritoneal/plasma barrier allows for direct and prolonged drug exposure with less systemic toxicity. These procedures, along with other methods used for peritoneal surface malignancies (PSMs), can be used in GCs with PMs as neoadjuvant chemotherapy or adjuvant treatments after radical surgery or as palliative treatments delivered either laparoscopically or—more recently—as pressurized intraperitoneal aerosol chemotherapy. The great heterogeneity of patients with stage IV gastric cancer did not allow us to carry out a systemic review; therefore, we limited ourselves to providing readers with an overview to clarify the indications and outcomes of integrated treatments for GCs with PMs by analyzing reports from the international clinical literature and the specific experiences of our oncoteam.