Preoperative assessment of peritoneal carcinomatosis: intraindividual comparison of 18F-FDG PET/CT and MRI.

Objective: Exact determination of localization and extent of peritoneal carcinomatosis (PC) before peritonectomy and hyperthermic intraperitoneal chemotherapy (HIPEC) is crucial for the clinical outcome. Our study compares dynamic contrast enhanced 3D MRI (T1wDCE) and 18F-FDG PET/CT regarding diagnostic accuracy in correlation with surgical exploration (SE) and histological (HI) results.

Materials And Methods: 15 patients with PC were examined on a 1.5T MRI and 16 slice PET/CT. MRI: coronal T1wDCE covering the complete abdomen (0.15 mmol Gd-chelate/kg BW, 2000 mL mannitol solution p.o., 40 mg buscopan i.v.). PET-CT: contrast enhanced 16slice CT (120 mL ultravist 370 i.v., 1000 mL mannitol solution p.o., 40 mg buscopan i.v.), PET: 350 MBq 18-FDG i.v., 3 min acquisition time/bed, 60 min after tracer injektion). Assessment by two independent, experienced observers in correlation with results of SE and HI for each abdominal segment based on the peritoneal cancer index (PCI) proposed by Sugarbaker and co-authors.

Results: MRI and PET/CT provided reliable detection of PC. One patient had to be excluded from statistical analysis. In summary, 182 segments were assessed (13/patient, 14 patients, one patient excluded from statistical analysis). PC was found in 118 by MRI, 124 by PET/CT. 4 segments were classified false positive for MRI, 2 for PET/CT. False negative segments (MRI: 17, PET/CT: 9) did not result in irresectability. Positive predictive value for PC/segment was 97/98%, negative predictive value 73/84%, sensitivity 87/93%, specificity 92/96%, and diagnostic accuracy 88/94% (MRI/PET/CT).

Conclusion: With high diagnostic accuracy for PC of both, MRI and PET/CT, PET/CT provides better diagnostic accuracy and especially better NPV.