External multicentre validation of pseudomyxoma peritonei PSOGI-Ki67 classification.

Area of Science:

• Oncology
• Pathology

Background:

• Pseudomyxoma peritonei (PMP) is a rare malignancy.
• Previous studies suggest Ki67 index addition to PSOGI PMP classification creates distinct HG-PMP subcategories with varied survival.
• This study validates this new classification externally and multicentrically.

Purpose of the Study:

• To externally and multicentrically validate the PSOGI-PMP classification incorporating the Ki67 proliferation index.
• To assess the predictive accuracy of the new classification for overall survival (OS) and disease-free survival (DFS).

Main Methods:

• Prospective analysis of a historical, international patient cohort (349 patients).
• Ki67 proliferation index determined in high-grade PMP (HG-PMP) samples.
• Statistical analysis included Cox proportional hazard models, Kaplan-Meier method, log-rank test, Harrel's C-index, and ROC curve analysis.

Main Results:

• The PSOGI-Ki67 classification showed significant differences in 5-year OS (LG-PMP: 86%, HG-PMP≤15: 59%, HG-PMP>15: 38%, SRC-PMP: 42%) and DFS (LG-PMP: 49%, HG-PMP≤15: 35%, HG-PMP>15: 16%, SRC-PMP: 18%).
• The classification demonstrated validated discrimination capability.
• The p-value for both OS and DFS was < 0.0001, indicating high statistical significance.

Conclusions:

• The PSOGI-Ki67 classification effectively discriminates and predicts OS and DFS in PMP patients.
• It accurately divides the HG-PMP category into two prognostically distinct subcategories.
• Routine incorporation of the Ki67 proliferation index into pathology reports for PMP patients is recommended.