Combined Diffusion-Weighted and Gadolinium-Enhanced MRI Can Accurately Predict the Peritoneal Cancer Index Preoperatively in Patients Being Considered for Cytoreductive Surgical Procedures

Abstract

To determine whether abdominal and pelvic magnetic resonance imaging (MRI) with diffusion-weighted and dynamic gadolinium-enhanced imaging can be used to accurately calculate the peritoneal cancer index (PCI) before surgery compared to the PCI tabulated at surgery. Thirty-three patients underwent preoperative MRI followed by cytoreductive surgery for primary tumors of the appendix (n = 25), ovary (n = 5), colon (n = 2), and mesothelioma (n = 1). MRIs were retrospectively reviewed to determine the MRI PCI. These scores were then compared to PCI tabulated at surgery. Patients were categorized as having small-volume tumors (PCI 0–9), moderate-volume tumors (PCI 10–20), and large-volume tumors (PCI > 20). The respective anatomic site scores for both MRI and surgery were compared. There was no significant difference between the MRI PCI and surgical PCI for the 33 patients (P = 0.12). MRI correctly predicted the PCI category in 29 (0.88) of 33 patients. Compared to surgical findings, MRI correctly predicted small-volume tumor in 6 of 7 patients, moderate-volume tumor in 3 of 4 patients, and large-volume tumor in 20 of 22 patients. MRI and surgical PCI scores were identical in 8 patients (24%). A difference of <5 was noted in 16 patients (49%) and of 5–10 in 9 patients (27%). Compared to surgical-site findings, MRI depicted 258 truly positive sites of peritoneal tumor, 35 falsely negative sites, 35 falsely positive sites, and 101 truly negative sites, with a corresponding sensitivity of 0.88, specificity of 0.74, and accuracy of 0.84. Combined diffusion-weighted and gadolinium-enhanced peritoneal MRI accurately predicts the PCI before surgery in patients undergoing evaluation for cytoreductive surgery.