Beyond Tumor Control: Radiation-Induced Ascites as a Rare Complication in Gastric Cancer Management

Gastric cancer is a leading cause of cancer-related mortality worldwide, with gastric adenocarcinoma as the predominant subtype. Multimodal treatment includes surgery, chemotherapy, and radiotherapy, which may rarely lead to complications such as ascites.

A 51-year-old male with poorly differentiated gastric adenocarcinoma of the pyloric region underwent chemotherapy and curative resection, achieving a complete pathological response. He subsequently received adjuvant radiotherapy (45 Gy in 25 fractions) and developed acute-onset ascites. Paracentesis yielded nonchylous fluid with elevated protein, lymphocytic predominance, and negative cytology. In the absence of validated thresholds for radiation-induced ascites, differentiation relied on excluding common causes using established parameters: serum-ascites albumin gradient (SAAG), polymorphonuclear (PMN) cell count, and adjunctive markers (e.g., ADA, triglycerides, amylase, and BNP) to rule out portal hypertensive, infectious, tuberculous, chylous, pancreatic, and cardiac etiologies. Comprehensive evaluation including PET imaging, repeat laparoscopy with peritoneal biopsies, and follow-up imaging revealed no recurrence or surgical complications. The ascites resolved after a single paracentesis without recurrence.

The diagnosis was made by exclusion, as the case is very rare and no specific biomarkers exist. Proposed mechanisms include endothelial injury, increased vascular permeability, and microthrombotic changes; however, evidence remains inferential.

This case underscores the importance of maintaining clinical vigilance for radiation-induced ascites in postradiotherapy patients and highlights the need for prospective studies to identify predictive biomarkers and optimize radiation field planning to minimize this rare but clinically significant complication.