Loco-regional staging of malignant pleural mesothelioma by integrated 18F-FDG PET/MRI

Abstract

Aim: To examine the performance of ¹⁸F-FDG PET/MRI in the loco-regional staging of malignant pleural mesothelioma (MPM).

Methods: Consecutive subjects with MPM undergoing pre-operative staging with ¹⁸F-FDG PET/CT who underwent a same day integrated ¹⁸F-FDG PET/MRI were prospectively studied. Clinical TNM staging (AJCC 7^th edition) was performed separately and in consensus by two readers on the ¹⁸F-FDG PET/MRI studies, and compared with staging by ¹⁸F-FDG PET/CT, and with final pathological stage, determined by a combination of intra-operative and histological findings.

Results: 10 subjects (9 male, mean age 68 years) with biopsy-proven MPM (9 epithelioid tumours, 1 biphasic) were included. One subject underwent neo-adjuvant chemotherapy between imaging and surgery and was excluded from the clinical versus pathological stage analysis. Pathological staging was concordant with staging by ¹⁸F-FDG PET/MRI in 67% (n = 6) of subjects, and with ¹⁸F-FDG PET/CT staging in 33% (n = 3). Pathological T stage was concordant with ¹⁸F-FDG PET/MRI in 78% (n = 7), and with ¹⁸F-FDG PET/CT in 33% (n = 3) of subjects. Pathological N stage was concordant with both ¹⁸F-FDG PET/MRI and ¹⁸F-FDG PET/CT in 78% (n = 7) of cases. No subject had metastatic disease. There was good inter-observer agreement for overall PET/MRI staging (weighted kappa 0.63) with moderate inter-reader agreement for T staging (weighted kappa 0.59). All 6 subjects with prior talc pleurodesis demonstrated mismatch between elevated FDG uptake and restricted diffusion in areas of visible talc deposition.

Conclusion: Clinical MPM staging by ¹⁸F-FDG PET/MRI is feasible, and potentially provides more accurate loco-regional staging than PET/CT, particularly in T staging.

Keywords: Fluorodeoxyglucose F18; Magnetic resonance imaging; Mesothelioma; Neoplasm; Positron emission tomography computed tomography; Staging.