Clinical utility of the peritoneal pathologic regression in gastric cancer patients associated to peritoneal metastasis. a study protocol

Objectives Peritoneal regression grade score (PRGS) has emerged a scoring system designed to measure the extent of residual disease following systemic or intraperitoneal therapies in patients with carcinomatosis. Higher (3–4) PRG-Scores match with a mediocre treatment response and prognosis. Conversely, lower grades (1–2) response are linked to significantly longer overall and progression-free survival periods. This study explores the utility of PRGS in assessing prognosis and optimizing therapeutic strategies for patients with peritoneal metastasis secondary to gastric malignancy. Methods This is a prospective cohort study, including patients with gastric cancer and peritoneal metastasis undergoing chemotherapy with intent for subsequent cytoreductive surgery. The primary endpoint of the study is to assess the pathological response of peritoneal involvement to primary chemotherapy according to the PRGS. Secondary objectives are to correlate PRGS with some clinical, pathological and molecular features (MMR, PDL1, CPS, HER2) as well as with other clinical and biochemical markers related to chemotherapy response. Results This protocol summarizes the current scientific evidence regarding the effectiveness of the PRGS in assessing peritoneal response to targeted therapies. It further hypothesizes its potential utility in evaluating the effects of systemic therapies for gastric cancer with peritoneal metastases, while also defining inclusion and exclusion criteria and outlining a flowchart for its implementation. Conclusions Our final endpoint is to expand PRGS applications to curative settings and identify factors such as tumor biology and chemotherapy regimens that may guide patient selection for adjuvant hyperthermic intraperitoneal chemotherapy (HIPEC) in gastric cancer with peritoneal metastasis.