Reproducibility of the Peritoneal Regression Grading Score (PRGS) for assessment of response to therapy in peritoneal metastasis

Abstract

Introduction

The 4‐tiered Peritoneal Regression Grading Score (PRGS) is assessing response to chemotherapy in peritoneal metastasis (PM). The PRGS is for example used to assess response to Pressurized IntraPeritoneal Aerosol Chemotherapy (PIPAC). However, the reproducibility of the PRGS is currently unkown. We aimed to evaluate the interobserver and intraobserver variability of the PRGS.

Materials and methods

33 patients who underwent at least 3 PIPAC treatments as part of the PIPAC‐OPC1 or PIPAC‐OPC2 clinical trials at Odense University Hospital, Denmark, were included. Prior to each therapy cycle, peritoneal quadrant biopsies were obtained, and three H&E stained step sections were scanned and uploaded to a pseudonymized web library. For determining the interobserver variability, eight pathologists assessed the PRGS for each quadrant biopsy, and Krippendorff's alpha and Intraclass Correlation Coefficients (ICCs) were calculated. For determining intraobserver variability, three pathologists repeated their own assessments, and Cohen's kappa and ICCs were calculated.

Results

A total of 331 peritoneal biopsies were analyzed. Interobserver variability for PRGS of each biopsy and for the mean and maximum PRGS per biopsy set was moderate to good/substantial. The intraobserver variability for PRGS of each biopsy and for the mean and maximum PRGS per biopsy set was good to excellent/almost perfect.

Discussion

Our data support the Peritoneal Regression Grading Score (PRGS) as a reproducible and useful tool to assess response to intraperitoneal chemotherapy in peritoneal metastasis. Future studies should evaluate the prognostic and predictive role of the PRGS.

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