Consensus Guideline for the Management of Colorectal Cancer with Peritoneal Metastases

Background The peritoneum is a common site of metastases from colorectal cancer (CRC), yet controversy exists regarding optimal treatment strategies. These guidelines describe the results of a national consensus addressing the management of CRC with peritoneal metastases (CRC-PM). Methods An update of the 2018 Chicago Consensus Guidelines was conducted using a modified Delphi technique. Two rounds of voting were performed to assess agreement levels on two clinical management pathways regarding synchronous and metachronous CRC-PM. Supporting evidence was evaluated via rapid literature reviews. Results The overall level of evidence was low in existing literature. Of 145 participants in the first round, 136 (96.8%) responded in the second round. Over 90% consensus was achieved in most pathway blocks. For both pathways, early referral to a peritoneal surface malignancy (PSM) center should be made for patients with CRC-PM. For the synchronous pathway, upfront cytoreductive surgery was de-emphasized in favor of systemic therapy. For the metachronous pathway, risk stratification via clinical and pathologic features was revised. For both pathways, surveillance strategies were added, including only a weak recommendation for circulating tumor DNA (ctDNA) testing given limited evidence of its utility in detecting and monitoring PM. Conclusion The consensus-driven clinical pathways provide valuable guidance for the management of CRC-PM. There remains a need for high-quality evidence and prospective multicenter trials in this domain. SYNOPSIS We developed two consensus-driven clinical pathways for the management of colorectal cancer with peritoneal metastases (CRC-PM), using a modified Delphi approach. Rapid reviews evaluating the optimal systemic therapy and the role of plasma-based liquid-biopsy for CRC-PM were conducted. ### Competing Interest Statement All competing interests will be provided in the final publication. ### Funding Statement This study did not receive any funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors