Concordance among radiological, laparoscopic and laparotomic peritoneal cancer index assessments in patients undergoing cytoreductive surgery for peritoneal metastases

Purpose Accurate preoperative estimation of the Peritoneal Cancer Index (PCI) is essential for optimal patient selection and surgical planning in peritoneal metastases. This study aimed to quantify the agreement between preoperative radiological PCI (rPCI) and laparoscopic PCI (lapPCI) compared with intraoperative laparotomic PCI (crsPCI) in patients undergoing cytoreductive surgery (CRS), and to explore the potential implications of PCI discordance for preoperative staging. Methods We conducted a retrospective cohort study including patients who underwent CRS for peritoneal metastases at a tertiary cancer center between August 2023 and February 2025. All patients had preoperative cross-sectional imaging, and a subset underwent diagnostic laparoscopy. Radiological PCI was retrospectively assigned by an experienced radiologist blinded to surgical findings. Agreement between rPCI, lapPCI, and crsPCI was assessed using intraclass correlation coefficients (ICC), Bland–Altman analysis, and correlation statistics. Results Fifty-six patients were included. Preoperative imaging consisted of MRI in 70% and CT in 30% of cases. Laparoscopic PCI was available in 16 patients (28.5%). The mean rPCI was 9.25 (IQR 3–13), compared with a mean crsPCI of 14.23 (IQR 9–18.5). Radiologic assessment showed good agreement with surgical PCI (ICC = 0.82; 95% CI 0.74–0.88), but systematically underestimated disease extent, with a mean bias of + 4.98 PCI units. Laparoscopic PCI demonstrated excellent agreement with crsPCI (ICC = 0.94; 95% CI 0.85–0.98) and minimal bias (− 1.5 PCI units). Correlation analyses supported these findings. Conclusion Radiologic PCI demonstrates good concordance with intraoperative findings but consistently underestimates tumor burden. In contrast, laparoscopic assessment provides excellent agreement with surgical PCI and offers valuable complementary information for preoperative staging. These results support a multimodal staging approach integrating radiologic and laparoscopic evaluation to improve accuracy in patient selection for CRS.