Impact of a modified peritoneal cancer index using FDG-PET/CT (PET-PCI) in predicting tumor grade and progression-free survival in patients with pseudomyxoma peritonei.

ABSTRACT

OBJECTIVES: The peritoneal cancer index (PCI) is widely used for assessing pseudomyxoma peritonei (PMP) in surgery. The aim of this study was to evaluate the utility of a modified PCI using 18F-fluorodeoxyglucose (18F-FDG)-PET/CT (PET-PCI) for predicting pathologic grade and progression-free survival (PFS) in patients with PMP. METHODS: Thirty-five patients who underwent 18F-FDG-PET/CT before cytoreductive surgery and/or hyperthermic intraperitoneal chemotherapy were enrolled. PET-PCI was determined by summing up the visually scored 18F-FDG uptake of PMP lesions in 13 specific abdominal-pelvic regions. Uptake score was defined as 0, no lesion or lesion without uptake; 1, slight uptake less than or equivalent to mediastinal blood pool; 2, moderate uptake above mediastinal but below or equal to liver; and 3, intense uptake moderately to markedly higher than liver. SUVmax of the lesion was also evaluated. RESULTS: Pathologic diagnosis revealed 19 patients with low-grade PMP and 16 patients with high-grade PMP. Patients with high-grade PMP showed significantly higher PET-PCI and SUVmax than patients with low-grade PMP (PET-PCI 14.8 vs. 8.7, p = 0.007; SUVmax 3.6 vs. 2.6, p = 0.013). Using a cutoff PET-PCI of 12, Kaplan-Meier analyses showed a significant difference in PFS between patients with high and low PET-PCI (p < 0.001; hazard ratio (HR), 12.4). For SUVmax, the optimal cutoff was 2.7 and the correlation with PFS was also significant (p = 0.008; HR, 4.7). In multivariate Cox proportional-hazards regression, PET-PCI was independently and significantly correlated with PFS. CONCLUSIONS: PET-PCI can reflect histopathologic features and appears useful for predicting recurrence in patients with PMP. KEY POINTS • Peritoneal cancer index using 18F-FDG-PET/CT (PET-PCI) has great potential for predicting progression-free survival in patients with pseudomyxoma peritonei. • PET-PCI provides higher prognostic performance than maximum standardized uptake value (SUVmax). • PET-PCI shows high correlation with histopathologic grade of pseudomyxoma peritonei.