Sarcopenia and outcomes after CRS ± HIPEC for gastric peritoneal metastases: no association with major morbidity and poorer survival in synchronous disease.

INTRODUCTION: We evaluated whether computed tomography (CT)-based body composition parameters predict outcomes after hyperthermic intraperitoneal chemotherapy (CRS ± HIPEC) for gastric peritoneal metastases (GPM). METHODS: A retrospective analysis of a prospectively maintained single-centre database included consecutive patients undergoing CRS ± HIPEC for GPM between January 2014 and December 2024. Skeletal muscle index (SMI), muscle radiodensity, and adipose tissue parameters were quantified on preoperative CT at the third lumbar vertebra. Sarcopenia was defined using validated sex-specific cut-offs. Postoperative complications, progression-free survival (PFS), and overall survival (OS) were analysed using multivariable regression and sensitivity analyses based on alternative sarcopenia definitions. RESULTS: Among 108 procedures performed in 106 included patients, 36 (33%) were sarcopenic. Major complications did not differ significantly (44% vs 39%; OR 1.26, 95% CI 0.56-2.83; p = 0.679), although moderate differences could not be excluded. In the overall cohort, neither PFS nor OS differed significantly according to sarcopenia status. However, among patients with synchronous GPM, sarcopenia was associated with shorter OS (median 10.2 vs 16.3 months; HR 1.85, 95% CI 1.05-3.25; p = 0.033), with a consistent but non-significant multivariable trend (p = 0.061). An adjusted interaction analysis supported effect modification according to disease timing (p for interaction = 0.043). Sensitivity analyses using four alternative sarcopenia definitions yielded consistent findings. CONCLUSION: Preoperative CT-defined sarcopenia identifies patients with synchronous GPM at higher risk of poor overall survival after CRS ± HIPEC without a detectable increase in postoperative morbidity. CT-based body composition may improve preoperative prognostic stratification and help identify candidates for future studies of nutritional optimisation or multimodal prehabilitation.