Staging peritoneal metastases in colorectal cancer: The correlation between MRI, surgical and histopathological peritoneal cancer index

DW-MRI is a non-invasive way to determine the peritoneal cancer index (PCI) in colorectal cancer (CRC) patients with peritoneal metastases (PM). However, like surgeons during surgery, radiologists struggle to differentiate between PM and fibrosis. This study aimed to investigate the agreement between the PCI as determined by MRI (mriPCI), during surgery (sPCI) and histopathology examination (pPCI) in CRC patients undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). This was a single-centre, retrospective study of CRC patients with PM who were staged with DW-MRI and underwent subsequent CRS-HIPEC. All initial patients' radiological, surgical and histopathology reports were reviewed for the PCI. Histopathology was the reference standard. Primary outcome was the correlation and agreement between mriPCI and pPCI. Eighty-seven patients were included. All patients had a complete macroscopic resection. Median (interquartile range) PCI for MRI, surgery, and histopathology were respectively 6.0 (2.5-9.0), 6.0 (4.0-11.0) and 6.0 (2.5-9.5). The intraclass correlation coefficient between the sPCI and pPCI was excellent 0.87 (p