Abstract
BACKGROUND: To intraindividually compare the diagnostic performance of positron emission computed tomography (F-18-FDG-PET/CT) and diffusion-weighted magnetic resonance imaging (DW-MRI) in a non-inferiority design for the discrimination of peripheral nerve sheath tumours as benign (BPNST), atypical (ANF), or malignant (MPNST) in patients with neurofibromatosis type 1 (NF1). RESULTS: In this prospective single-centre study, thirty-four NF1 patients (18 male; 30 ± 11 years) underwent F-18-FDG-PET/CT and multi-b-value DW-MRI (11 b-values 0 - 800 s/mm²) at 3T. Sixty-six lesions corresponding to 39 BPNST, 11 ANF, and 16 MPNST were evaluated. Two radiologists independently assessed the maximum standardized uptake value (SUV(max)) and mean and minimum apparent diffusion coefficient (ADC(mean/min)) as well as the ADC in areas of lowest signal intensity in each lesion (ADC(dark)). The AUCs of DW-MRI and F-18-FDG-PET/CT were compared to determine whether the ADC is non-inferior to SUV(max) (non-inferiority margin equal to -10%). Follow-up of ≥ 24 months (BPNST) or histopathological evaluation (MPNST + ANF) served as diagnostic reference standard. Both SUV(max) and ADC parameters demonstrated good diagnostic accuracy (AUC(SUVmax) 94.0%; AUC(ADCmean/min/dark) 91.6% / 90.1% / 92.5%). However, non-inferiority could not be demonstrated for any of the three ADC parameters (lower limits of the confidence intervals of the difference between the AUC of ADC(mean/min/dark) and SUV(max) -12.9% / -14.5% / -11.6%). Inter-rater reliability was excellent for both imaging techniques (Krippendorff's alpha all > 0.94). CONCLUSIONS: Both PET/CT-derived SUV(max) and MRI-derived ADC allow sensitive and non-invasive differentiation of benign and (pre)-malignant peripheral nerve sheath tumours. Nevertheless, DW-MRI cannot be considered as non-inferior to F-18-FDG-PET/CT in this prospective single-centre study.