Objectives: This study investigated the correlation between the peritoneal carcinomatosis index (PCI) and patient outcome depending on the tumour type.
Background: Peritoneal surface malignancy (PSM) treatment depends on tumour type. Mucinous PSM (m-PSM) is associated with a better prognosis than non-mucinous PSM (nm-PSM). The PCI's predictive ability has not yet been evaluated.
Methods: We analysed 123 patients with PSM treated with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) between 2008 and 2015. The m-PSM group (n = 75) included patients with appendiceal cancer (n = 15), colorectal cancer (n = 21), or low-grade appendiceal mucinous neoplasm (n = 39); the nm-PSM group (n = 48) included patients with gastric (n = 18) or colorectal (n = 30) cancer. The PCI's predictive ability was evaluated by multiple Cox-proportional hazard regression analysis and Kaplan-Meier curves.
Results: The 5-year survival and PCI were higher in m-PSM patients (67.0%; 20.5 ± 12.1) than in nm-PSM patients (32.6%; p = 0.013; 8.9 ± 6.0; p < 0.001). Colorectal nm-PSM patients with PCI ≥16 had a worse 2-year survival (25.0%) vs. patients with PCI <16 (79.1%; log rank = 0.009), but no significant effect was observed in patients with m-PSM (66.7% vs. 68.1%; p = 0.935). Underlying disease (HR 5.666-16.240), BMI (HR 1.109), and PCI (HR 1.068) significantly influenced overall survival in all patients.
Conclusions: PCI is prognostic in nm-PSM, but not in m-PSM. CRS and HIPEC may benefit not only patients with low PCI, but also those with high PCI and m-PSM.
Keywords: Cytoreductive surgery; HIPEC; mucinous adenocarcinoma; peritoneal cancer index.