NeoRes Study - Preoperative Chemotherapy in Colorectal Peritoneal Disease Prior to Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy (HIPEC)

Study Title: Neores Study - Evaluating Systemic Chemotherapy Efficacy in Colorectal Peritoneal Metastases Principal Investigator: Peter Cashin Akademiska sjukhuset / Uppsala universitet Background: Peritoneal metastases from colorectal cancer are often associated with poorer outcomes compared to other metastatic sites. While systemic chemotherapy is widely used as a neoadjuvant treatment prior to CRS (Cytoreductive Surgery) and HIPEC (Hyperthermic Intraperitoneal Chemotherapy), its efficacy specifically for peritoneal metastases remains underexplored. Current practice in many countries includes neoadjuvant therapy to evaluate tumor biology and attempt tumor downstaging before surgery, despite the lack of robust data supporting this approach in colorectal cancer. Purpose and Aims: The study aims to evaluate how effective systemic chemotherapy is in treating isolated peritoneal metastases in colorectal cancer patients. The protocol defines two specific populations: Patients receiving upfront systemic conversion chemotherapy. Patients undergoing open/close laparotomy (non-resectable disease found during surgery). Key Research Questions: What is the response rate to systemic chemotherapy before surgery? How many patients progress to CRS+HIPEC? What is the prognosis of those not undergoing surgery? How effective is FMCA (Fluorometric Microculture Cytotoxicity Assay) in predicting chemotherapy sensitivity? Do patients treated with FMCA-guided sensitive chemotherapy have better outcomes? Methods: This is a retrospective chart review study based on patient data from 2004-2021. It includes: Review of HIPEC MDT (multidisciplinary team) conference notes to identify patients recommended for neoadjuvant conversion therapy. Review of open/close laparotomy cases with FMCA testing. Inclusion Criteria: For HIPEC Pathway: Colorectal cancer with isolated peritoneal metastases. Patients recommended for systemic chemotherapy before CRS+HIPEC. For Open/Close Pathway: I