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

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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: Isolated peritoneal metastases discovered during surgery. Successful FMCA analysis performed. Updated Inclusion (2024): Patients with simultaneously resectable liver, para-aortal, and lung metastases are now allowed. Exclusion Criteria (both pathways): Appendiceal cancer. Retroperitoneal lymph node metastases. Other systemic metastases (liver, lung, brain, bone, etc.), unless resectable under updated criteria. Data Collection: Patient data will be retrieved from: Uppsala University Hospital records Nationella Patientöversikten (national electronic health record) Swedish patient registry Swedish Colorectal Cancer Registry (SCRCR) (especially for molecular markers like KRAS, NRAS, BRAF, PIK3CA, MMR) When data is incomplete, referral hospitals will be contacted to gather additional information on administered chemotherapy (first and second-line therapies), therapy response, and survival outcomes. Endpoints: For chemotherapy group: Response to therapy and conversion to CRS+HIPEC. For open/close group: Progression-free survival and overall survival. Evaluation of FMCA sensitivity prediction accuracy. Outcomes based on whether patients received FMCA-indicated sensitive or resistant chemotherapy. Statistical Methods: Descriptive statistics. Kaplan-Meier survival curves. Cox proportional hazards models. Clinical Significance: There is a clear lack of high-quality evidence evaluating systemic chemotherapy's role in isolated peritoneal metastases. Despite being widely used, neoadjuvant therapy may not significantly improve survival outcomes in these cases, as seen in analogous ovarian cancer settings. The Neores study seeks to clarify the real-world effectiveness of this approach and to evaluate whether FMCA-guided treatment has clinical utility in predicting treatment success. Given the uniqueness of Uppsala's long-standing use of FMCA, the study could provide important insights for patient selection and personalized therapy decisions.

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