Gastric cancer peritoneal metastases as an immune compartment: immune evasion, systemic immunotherapy and regional treatment strategies
- 1Department of Upper Gastrointestinal Surgery, Beaumont Hospital
Abstract
Gastric cancer peritoneal metastasis (GCPM), particularly associated with diffuse and poorly cohesive cancers, in which tumour cells grow singly or in small, loosely associated groups, presents an anatomical and immunological treatment challenge. This review examines the peritoneal surface and surrounding fluid as an interacting immune compartment comprising tumour implants, malignant ascites, free tumour cells, stroma and immune populations. Human studies identify cytotoxic-cell depletion or exhaustion, macrophage-rich ascites and suppressive soluble mediators; experimental findings support complement-pathway involvement in immune-checkpoint ligand expression. These observations offer a biological explanation for impaired local immunity but do not establish clinical resistance to checkpoint inhibition. Systemic therapy remains the treatment backbone, yet pivotal trials rarely report the Peritoneal Cancer Index (PCI), cytology, ascites response or peritoneal-specific progression. Early studies combine checkpoint blockade with pressurised intraperitoneal aerosol chemotherapy (PIPAC), repeated intraperitoneal paclitaxel or hyperthermic intraperitoneal chemotherapy (HIPEC); direct intraperitoneal antibodies, cytokines and cellular therapies are also under investigation. Feasibility and local pharmacodynamic changes do not establish synergistic benefit. Future trials should compare an added intraperitoneal treatment against an otherwise identical systemic regimen, collect matched blood, ascites and peritoneal tissue samples over time, and relate immune changes to cytological clearance, PCI, symptoms and survival. Operative consolidation requires a separate randomised assessment in prospectively defined responders. Treatment continuity, quality of life, nutrition and hospital-free survival are essential measures of net benefit.
Related
- Incidence, treatment, and survival of synchronous peritoneal metastases in breast cancer
- A Contemporary Review of Resectability and Treatment Strategies for Colorectal Liver Metastases: Part 2-Advanced Surgical Techniques, Conversion Strategies, and the Expanding Boundaries of Treatment.
- A Contemporary Review of Resectability and Treatment Strategies for Colorectal Liver Metastases: Part 1—Diagnosis, Defining Resectability, and Management of Upfront Resectable and Synchronous Disease
- High intestinal obstruction secondary to peritoneal metastases from invasive lobular breast carcinoma: A case report of an unusual presentation
- Exploring immunotherapy resistance in bone metastasis: mechanisms and optimization of combined treatment strategies-a narrative review.
BibTeX
@article{burke2026gastric,
title = {{Gastric cancer peritoneal metastases as an immune compartment: immune evasion, systemic immunotherapy and regional treatment strategies}},
author = {Eoghan Burke},
journal = {Frontiers in Oncology},
year = {2026},
month = oct,
doi = {10.3389/fonc.2026.1980560},
url = {https://www.frontiersin.org/articles/10.3389/fonc.2026.1980560/full},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Gastric cancer peritoneal metastases as an immune compartment: immune evasion, systemic immunotherapy and regional treatment strategies
AU - Eoghan Burke
PY - 2026
DA - 2026/10/15
JO - Frontiers in Oncology
DO - 10.3389/fonc.2026.1980560
UR - https://www.frontiersin.org/articles/10.3389/fonc.2026.1980560/full
AB - Gastric cancer peritoneal metastasis (GCPM), particularly associated with diffuse and poorly cohesive cancers, in which tumour cells grow singly or in small, loosely associated groups, presents an anatomical and immunological treatment challenge. This review examines the peritoneal surface and surrounding fluid as an interacting immune compartment comprising tumour implants, malignant ascites, free tumour cells, stroma and immune populations. Human studies identify cytotoxic-cell depletion or exhaustion, macrophage-rich ascites and suppressive soluble mediators; experimental findings support complement-pathway involvement in immune-checkpoint ligand expression. These observations offer a biological explanation for impaired local immunity but do not establish clinical resistance to checkpoint inhibition. Systemic therapy remains the treatment backbone, yet pivotal trials rarely report the Peritoneal Cancer Index (PCI), cytology, ascites response or peritoneal-specific progression. Early studies combine checkpoint blockade with pressurised intraperitoneal aerosol chemotherapy (PIPAC), repeated intraperitoneal paclitaxel or hyperthermic intraperitoneal chemotherapy (HIPEC); direct intraperitoneal antibodies, cytokines and cellular therapies are also under investigation. Feasibility and local pharmacodynamic changes do not establish synergistic benefit. Future trials should compare an added intraperitoneal treatment against an otherwise identical systemic regimen, collect matched blood, ascites and peritoneal tissue samples over time, and relate immune changes to cytological clearance, PCI, symptoms and survival. Operative consolidation requires a separate randomised assessment in prospectively defined responders. Treatment continuity, quality of life, nutrition and hospital-free survival are essential measures of net benefit.
SN - 2234-943X
ER -