BACKGROUND AND PURPOSE: Diffuse intrinsic pontine glioma is a devastating childhood cancer that despite being primarily diagnosed by MR imaging alone, lacks robust prognostic imaging features. This study investigated patterns and quantification of extrapontine lesion extensions as potential prognostic imaging biomarkers for survival in children with newly diagnosed diffuse intrinsic pontine glioma. MATERIALS AND METHODS: Volumetric analysis of baseline MR imaging studies was completed in 131 patients with radiographically defined typical diffuse intrinsic pontine gliomas. Extrapontine tumor extension was classified according to the direction of extension: midbrain, medulla oblongata, and right and left middle cerebellar peduncles; various extrapontine lesion extension patterns were evaluated. The Kaplan-Meier method was used to estimate survival differences; linear regression was used to evaluate clinical-radiographic variables prognostic of survival. RESULTS: At least 1 extrapontine lesion extension was observed in 125 patients (95.4%). Of the 11 different extrapontine lesion extension patterns encountered in our cohort, 2 were statistically significant predictors of survival. Any extension into the middle cerebellar peduncles was prognostic of shorter overall survival (P 4 .01), but extension into both the midbrain and medulla oblongata but without extension into either middle cerebellar peduncle was prognostic of longer overall survival compared with those having no extension (P 4 .04) or those having any other pattern of extension (P , .001). CONCLUSIONS: Within this large cohort of patients with typical diffuse intrinsic pontine gliomas, 2 specific extrapontine lesion extension patterns were associated with a significant overall survival advantage or disadvantage. Our findings may be valuable for risk stratification and radiation therapy planning in future clinical trials. ABBREVIATIONS: DIPG 4 diffuse intrinsic pontine glioma; EPLE 4 extrapontine lesion extension; ETV 4 extrapontine tumor volume; MCP 4 middle cerebellar peduncle; OS 4 overall survival; PFS 4 progression-free survival; PTV 4 pontine tumor volume; RT 4 radiation therapy; TTV 4 total tumor volume H igh-grade gliomas comprise 10%-15% of pediatric brain tumors and cause half of the deaths occurring as a result of CNS neoplasms in children. 1,2 Of pediatric high-grade gliomas, those occurring in the pons, formerly referred to as diffuse intrinsic pontine glioma (DIPG), are most common and have the worst prognosis, with a 2-year survival rate of ,10%. 2,3
Background and Purpose
The conventional MRI appearance of diffuse intrinsic pontine glioma suggests intralesional histopathological heterogeneity, and various distinct lesion components, including T2-hypointense foci, have been described. Here we report the prevalence, conventional MRI semiology, and advanced MRI features of non-necrotic T2-hyperintense foci within diffuse intrinsic pontine glioma.
Materials and Methods
Twenty-five patients with diffuse intrinsic pontine glioma were included in this study. MRI studies were performed at 3T by using conventional and advanced MRI sequences. Perfusion (CBV), vascular permeability (ve, Ktrans) and diffusion (ADC) metrics were calculated and used to characterize non-necrotic T2-hyperintense foci in comparison with other lesion components, namely necrotic T2-hyperintense foci, T2-hypointense foci, peritumoral edema, and normal brainstem. Statistical analysis was performed by using Kruskal–Wallis and Wilcoxon rank sum tests.
Results
Sixteen non-necrotic T2-hyperintense foci were found in 12 tumors. In these foci, ADC values were significantly higher than those in either T2-hypointense foci (P=.002) or normal parenchyma (P=.0002), and relative CBV values were significantly lower than those in either T2-hypointense (P=.0002) or necrotic T2-hyperintense (P=.006) foci. Ktrans values in T2-hyperintense foci were lower than those in T2-hypointense (P=.0005) or necrotic T2-hyperintense (P=.0348) foci.
Conclusion
Non-necrotic T2-hyperintense foci are common, distinct lesion components within diffuse intrinsic pontine glioma. Advanced MR data suggest low cellularity and an early stage of angioneogenesis with leaky vessels resulting in expansion of the extracellular space. Because of the lack of biopsy validation, the underlying histoarchitectural and pathophysiological changes remain unclear; therefore, these foci may correspond to a poorly understood biological event in tumor evolution.
BACKGROUND AND PURPOSE: Radiation necrosis, for which abnormal WM enhancement is a hallmark, is an uncommon complication of craniospinal irradiation in children with medulloblastoma. The magnetization transfer ratio measures macromolecular content, dominated by myelin in the WM. We investigated whether the pretreatment supratentorial (nonsurgical) WM magnetization transfer ratio could predict patients at risk for radiation necrosis after radiation therapy for medulloblastoma.
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