The Role of Additional Staining in the Assessment of the PRGS in Peritoneal Metastasis of Gastric Cancer

Authors:
Wiebke SOLASS^1,2,4 , Giorgi NADIRADZE^2,3 , Marc A REYMOND^2,3 , Hans BÖSMÜLLER^1,2


Affliations:
¹Institute of Pathology and Neuropathology, University Hospital Tübingen, Eberhard-Karls-University Tübingen, Germany
²National Center for Pleura and Peritoneum, University of Tuebingen, Germany
³Dept. of General and Transplant Surgery, University Hospital Tübingen, Eberhard-Karls-University Tübingen, Germany
⁴Institute of Pathology, University Bern, Switzerland


Corresponding email address:
Corresponding Author: Wiebke SOLASS (wiebke.solass@t-online.de)

Abstract

The Peritoneal Regression Grading Score (PRGS) is four tied histological regression grading system to determine the therapy response of peritoneal metastasis (PM) to chemotherapy. The scoring is performed on conventional Hematoxylin and Eosin (HE) stain. But, in some biopsies, the PRGS scoring is challenging, especially in gastric cancer. Additionally, in PRGS 1 cases (no residual tumor cells detectable in HE) the minimal residual tumor might be overseen. In this study, we investigated the influence of additional stainings on PRGS evaluation. Three hundred thirty-nine biopsies were obtained during 76 laparoscopies in 33 patients with PM of gastric cancer. All biopsies were classified according to the PRGS recommendation of 2016 in HE stain. After that, all biopsies ranked PRGS 1 or indefinite for diagnosis were stained with PAS and afterwards, the remaining indefinite or PRGS 1 cases were also stained with BerEP4. This sequential approach allowed the detection of residual tumor cells in 15% of cases and changed the response assessment in 21% of patients. Therefore, we recommend the additional staining with PAS and/or BerEP4 in all PRGS 1 or unclear cases.