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External multicentre validation of pseudomyxoma peritonei PSOGI-Ki67 classification
A Arjona-Sanchez1, A Martinez-López2, M T Moreno-Montilla3
1Unit of Surgical Oncology, Department of Surgery, Reina Sofia University Hospital, Spain; Maimonides Biomedical Research Institute of Cordoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Cordoba, Spain. Electronic address: https://twitter.com/alarjosan.
Background:
Pseudomyxoma peritonei (PMP) is a rare malignant disease. Adding of the Ki67 proliferation index to the PSOGI PMP classification provided two different subcategories of the extensive HG-PMP group (HG-PMP ≤15% and HG-PMP >15%) with different survival in a previous unicentric study. This study aims to carry out an external and multicentre validation of this new proposed classification.
Method:
It was a prospective analysis of samples from a historical and international cohort of patients. A representative area with higher cellular density was used to determine the Ki67%. The Ki67 proliferation index (%) was determined in all the HG-PMP patients. A Cox proportional hazard models and multivariable COX models were used. The Kaplan-Meier method and the two-tailed log-rank test were used to analyse the effect of different PSOGI-Ki67 categories on OS and DFS. Its predictive accuracy was analysed using Harrel's C-index and the ROC curve. The calibration was performed using the calibration plots matching.
Results:
After exclusions, 349 patients were available for analysis. The 5-years OS were 86% for LG-PMP, 59% for HG-PMP≤15, 38% for HG-PMP>15 and 42% for SRC-PMP (p = 0.0001). The 5-years DFS were 49% for LG-PMP, 35% for HG-PMP≤15, 16% for HG-PMP>15 and 18% SRC-PMP (p = 0.0001). The discrimination capability of PSOGI-Ki67 was validated.
Conclusion:
the PSOGI-Ki67 classification discriminates and predicts the OS and DFS in patients with PMP dividing the HG-PMP category into two well-defined sub-categories. The Ki67 proliferation index should be incorporated routinely in the pathology report for these patients.
Insights
The Ki67 proliferation index refines the Pseudomyxoma Peritonei (PMP) classification, improving survival prediction for high-grade PMP (HG-PMP). This validated PSOGI-Ki67 classification is crucial for patient management.
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.
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