Does elevated glucose metabolism correlate with higher cell density in Neurofibromatosis type 1 associated peripheral nerve sheath tumors?

PURPOSE: To investigate whether elevated glucose metabolism in neurofibroma, determined by [F18]-FDG-PET, is correlated with cell density in MRI, as expressed through the apparent diffusion coefficient. MATERIALS AND METHODS: Patients diagnosed with neurofibromatosis type 1 and peripheral nerve sheath tumors (PNST) were enrolled in this prospective, IRB-approved study. After a single [F18]-FDG injection, patients consecutively underwent [F18]-FDG-PET/CT and [F18]-FDG-PET/MRI on the same day. Maximum and mean standardized uptake values (SUVmax, SUVmean) on [F18]-FDG-PET/CT and [F18]-FDG-PET/MRI were compared, and correlated with minimum and mean apparent diffusion coefficients (ADCmean, ADCmin). RESULTS: A total of 12 (6 male/6 female, mean age was 16.2 ± 5.2 years) patients were prospectively included and analyzed on a per-lesion (n = 39) basis. The SUVmean of examined PNST showed a moderate negative correlation with the ADCmean (r = -.441) and ADCmin (r = -.477), which proved to be statistically significant (p = .005 and p = .002). The SUVmax of the respective lesions, however, showed a weaker negative correlation for ADCmean (r: -.311) and ADCmin (r: -.300) and did not reach statistical significance (p = .054 and p = .057). Lesion-based correlation between [F18]-FDG-PET/MRI and [F18]-FDG-PET/CT showed a moderate correlation for SUVmax (r = .353; p = .027) and a strong one for SUVmean (r = .879; p = .001)). Patient-based liver uptake (SUVmax and mean) of [F18]-FDG-PET/MRI and [F18]-FDG-PET/CT were strongly positively correlated (r = .827; p < .001 and r = .721; p < .001) but differed significantly (p < .001). CONCLUSIONS: We found a statistically significant, negative correlation between glucose metabolism and cell density in PNST. Thus, ADCmean and ADCmin could possibly add complimentary information to the SUVmax and SUVmean and may serve as a potential determinant of malignant transformation of PNST.