MR Imaging Characteristics and ADC Histogram Metrics for Differentiating Molecular Subgroups of Pediatric Low-Grade Gliomas.

BACKGROUND AND PURPOSE

and type 1 neurofibromatosis status are distinctive features in pediatric low-grade gliomas with prognostic and therapeutic implications. We hypothesized that DWI metrics obtained through volumetric ADC histogram analyses of pediatric low-grade gliomas at baseline would enable early detection of and type 1 neurofibromatosis status.

MATERIALS AND METHODS

We retrospectively evaluated 40 pediatric patients with histologically proved pilocytic astrocytoma ( = 33), ganglioglioma ( = 4), pleomorphic xanthoastrocytoma ( = 2), and diffuse astrocytoma grade 2 ( = 1). Apart from 1 patient with type 1 neurofibromatosis who had a biopsy, 11 patients with type 1 neurofibromatosis underwent conventional MR imaging to diagnose a low-grade tumor without a biopsy. molecular analysis was performed for patients without type 1 neurofibromatosis. Eleven patients presented with V600E-mutant, 20 had rearrangement, and 8 had wild-type tumors. Imaging studies were reviewed for location, margins, hemorrhage or calcifications, cystic components, and contrast enhancement. Histogram analysis of tumoral diffusivity was performed.

RESULTS

Diffusion histogram metrics (mean, median, and 10th and 90th percentiles) but not kurtosis or skewness were different among pediatric low-grade glioma subgroups (< .05). Diffusivity was lowest in V600E-mutant tumors (the 10th percentile reached an area under the curve of 0.9 on receiver operating characteristic analysis). There were significant differences between evaluated pediatric low-grade glioma margins and cystic components ( = .03 and = .001, respectively). Well-defined margins were characteristic of or wild-type rather than V600E-mutant or type 1 neurofibromatosis tumors. None of the type 1 neurofibromatosis tumors showed a cystic component.

CONCLUSIONS

Imaging features of pediatric low-grade gliomas, including quantitative diffusion metrics, may assist in predicting and type 1 neurofibromatosis status, suggesting a radiologic-genetic correlation, and might enable early genetic signature characterization.