Real-world risk factors for incomplete cytoreduction in peritoneal carcinomatosis patients scheduled for cytoreductive surgery and hyperthermic intraperitoneal chemotherapy

Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) is a treatment option for selected patients with peritoneal carcinomatosis. This study investigates preoperative factors influencing incomplete CRS. We retrospectively reviewed 188 patients scheduled for curative-intent CRS/HIPEC between April 2015 and May 2023. Preoperative peritoneal cancer index (PCI) scores were determined using computed tomography (CT) (n = 155) and/or magnetic resonance imaging (MRI) (n = 82). Complete CRS was achieved in 126 patients (67.0%) and incomplete CRS in 62 (32.9%). Colorectal cancer was the predominant primary tumor (complete CRS: 42.9%; incomplete CRS: 50.0%), followed by ovarian cancer (34.1% vs. 17.7%). Multivariate analysis revealed imaging-specific risk factors: the CT model identified ascites (OR = 4.57) and higher PCI scores in regions 0 and 11, while the MRI model identified prior chemotherapy (OR = 101.06) and higher PCI scores in regions 2, 3, and 11. Decision tree analysis showed ascites altered PCI thresholds for patients with ascites (CT: 18.5, MRI: 6.5) versus without (CT: 8.5, MRI: 12.5). Both imaging modalities demonstrated moderate agreement with surgical findings for total PCI scores (ICC = 0.656 and 0.678), with stronger correlations in regions 0–8 than regions 9–12. Small bowel regions showed poor accuracy, with lowest sensitivity in region 11. Ascites and higher PCI scores in specific regions identified on preoperative imaging were associated with increased risk of incomplete CRS. These findings can improve patient selection and preoperative planning for CRS/HIPEC in peritoneal carcinomatosis.