Diffusion-weighted magnetic resonance imaging versus surgical staging in patients with colorectal peritoneal metastases: The multicenter, international, randomized controlled DISCO trial.

15 Background: In patients with colorectal peritoneal metastases (CPM), cytoreductive surgery (CRS) can prolong survival at the cost of a substantial risk of major morbidity. Accurate staging is crucial to identify who is most likely to benefit from CRS. Computed tomography (CT) often underestimates the extent of disease, necessitating additional staging laparoscopy. This randomized controlled trial (RCT) investigated whether preoperative diffusion-weighted magnetic resonance imaging (DW-MRI) could reduce futile surgical procedures. Methods: This was an international multicenter RCT of patients with CPM eligible for CRS after CT staging in seven Dutch centers (Dutch cohort) and one Chinese center (Fudan cohort). Patients were randomly assigned 1:1 to either DW-MRI-based staging (DW-MRI group) or standard staging with or without laparoscopy (control group) via a web-based randomization system, stratified by center. In the DW-MRI group, patients were categorized by peritoneal cancer index (PCI) on DW-MRI: 24 contraindicated CRS. The primary endpoint was the proportion of futile surgical procedures between groups, analyzed with the chi-squared test. Futile surgical procedures were defined as all surgical procedures in patients with inoperable disease (surgical PCI >24 during staging laparoscopy, >20 at initiation of CRS, incomplete CRS, or no malignancy) or staging laparoscopies in patients with limited disease (surgical PCI