Editorial questions PCI as a stand-alone response measure in gastric peritoneal metastases

The editorial reviews a study by Kalmbach et al. of 69 patients with synchronous gastric or gastroesophageal junction cancer peritoneal metastases who underwent paired operative PCI assessments after systemic chemotherapy, predominantly FLOT. PCI decreased in 23 patients, was unchanged in seven and increased in 39. Forty-four patients underwent gastrectomy, and 23 achieved CC-0 cytoreduction. The editorial notes that imaging may underestimate peritoneal disease and that PCI scoring can vary between observers and operative assessments.

The authors caution that PCI measures anatomical disease burden, not necessarily biological response: treated implants may remain visible as fibrosis, while apparent disappearance may not exclude microscopic disease. They propose interpreting PCI alongside the peritoneal regression grading score (PRGS), cytology and the achievement of CC-0 resection. They also cite the phase III DRAGON-01 trial, in which intraperitoneal paclitaxel plus intravenous paclitaxel and S-1 improved median overall survival versus the systemic regimen alone (19.4 vs. 13.9 months; HR 0.67) in patients with peritoneal-only metastases.

This is an editorial, not a new clinical study, and it does not establish a validated surrogate endpoint or justify changing treatment. The authors call for standardized PCI assessment, mapped biopsies and cytology in future trials. Overall survival, progression-free survival, morbidity and quality of life remain key outcomes; the editorial reports no funding or conflict-of-interest disclosures.