Peritoneal sampling and histological assessment of therapeutic response in peritoneal metastasis: proposal of the Peritoneal Regression Grading Score (PRGS)

Abstract

Background: Multimodal therapeutic strategies have improved the outcome of peritoneal metastases (PM). However, objective assessment of therapy response remains difficult in PM, since radiological studies have a poor accuracy for low-volumetric disease. There is an obvious need for a histological gold standard allowing assessment of tumor response to treatment in PM.Content: We propose to perform peritoneal punch biopsies with a diameter of 3 to 5 mm in all four abdominal quadrants. We propose a four-tier Peritoneal Regression Grading Score (PRGS), defined as Grade 1: complete response (absence of tumor cells), Grade 2: major response (major regression features, few residual tumor cells), Grade 3: minor response (some regressive features but predominance of residual tumor cells), Grade 4: no response (tumor cells without any regressive features). Acellular mucin and infarct-like necrosis should be regarded as regression features. We recommend reporting the mean and the worst value of the regression grades obtained. When complete tumor response is suspected intraoperatively, a peritoneal cytology should be sampled.Summary: A generic, unique score for the assessment of histological tumor response to chemotherapy in PM makes sense because of the clinical impact of histological response to therapy and because the organ of metastasis (peritoneum) is the same. By adopting PRGS, different centers will be able to use a uniform terminology and grading that will allow meaningful comparison of their results.Outlook: PRGS has now to be validated in several gastrointestinal and gynecological cancer types and may be useful both in clinical and research settings.

Electrostatic precipitation Pressurized IntraPeritoneal Aerosol Chemotherapy (ePIPAC): first in-human application

“…However, CT-scans showed an objective tumor regression in 2 patients and stable disease in the third patient according to RECIST criteria, which all were unexpected in this kind and stage of peritoneal disease. Further evidence for a potential efficacy of ePIPAC in PM of HBP origin was delivered by repeated histology, which showed complete regression of peritoneal disease in 2 patients and major regression in the third one according to PRGS [22]. After (e)PIPAC, secondary curative surgery (R0) could be performed in one patient with metastatic cancer of the pancreas tail and no evidence of peritoneal metastasis was found during surgery, all peritoneal histologies remaining negative.…”

“…Clinical, laboratory and anatomopathology data were documented according to GCP rules, including electronic microfilm archiving and digital video recording of the surgical procedures. Tumor response was graded by independent pathologists considering fibrosis overgrowth and proportion of vital tumor cells, as described elsewhere [22]. Adverse events were classified according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0 [23].…”

Reproducibility of the peritoneal regression grading score for assessment of response to therapy in peritoneal metastasis

“…All slides were analysed online by eight independent pathologists from different institutes and different countries with diverse levels of practical experience in the assessment of histological regression grading in PM. Four of the participating pathologists were co‐authors of the proposal article regarding the PRGS . The other four pathologists were trained to become familiar with the PRGS system and were given a copy of the reference publication .…”

“…Most published scoring systems for the assessment of the histological response to neoadjuvant treatment are based on surgical resection specimens of the primary tumour or metastases . In 2016, the four‐tiered peritoneal regression grading score (PRGS) for the histological assessment of response to therapy in peritoneal metastasis (PM) was proposed by a group of European pathologists . The PRGS is potentially clinically important in the assessment of histological response to intraperitoneal chemotherapy, particularly when such a therapy is given several times and the decision as to whether the patient should receive additional treatment depends on the histological response.…”

Recommendations for pathological diagnosis on biopsy samples from peritoneal dialysis patients

“…to check pathological status associated with concurrent PD therapy. Although laparoscopic surgery is not required for removing a PD catheter, the images gained could be useful with regards to any underlying malignant disease [20][21][22]. There are few studies about macroscopic findings on PD patients, however, a scoring system including taking into account peritoneal appearance, hypervascular changes, adhesions and encapsulation may be useful [23,24].…”