NIMG-71. DIFFUSION CHARACTERISTICS OF PEDIATRIC DIFFUSE MIDLINE GLIOMAS WITH HISTONE H3 K27M MUTATION USING APPARENT DIFFUSION COEFFICIENT HISTOGRAM ANALYSIS

Abstract

PURPOSE

Diffuse midline gliomas with histone H3 K27M mutation are a new group of gliomas diagnostic entity as of the 2016 WHO guidelines. We previously showed no difference between wildtype and K27M mutant midline tumors in their enhancement patterns, border characteristics, and presence of necrosis on clinical protocol MRI. Herein, we evaluated the use of diffusion weighted imaging as a mechanism to distinguish histone H3 K27M mutant from wildtype midline gliomas.

MATERIALS AND METHODS

44 pediatric patients (<21 years old) with diffuse midline gliomas were confirmed with histone H3 K27M mutation testing. In 31 eligible patients, whole tumor voxel based ADC histograms were generated and evaluated.

RESULTS

Among 18 intratentorial and 13 supratentorial gliomas, 23 (74%) of the tumors were histone H3 K27M mutant. There was no difference between the K27M mutant and wildtype midline gliomas with respect to tumor ADC mean, median, minimum, maximum, or 1 ^st to 99 ^th percentiles. Average ADC values for diffuse midline gliomas were 1.28 x10 ^-3 mm ²/sec (95% CI 1.21, 1.34). Patients who survived less than one year after diagnosis have lower median ADC values (1.10 x 10 ^-3 mm ²/sec, 95% CI 0.90, 1.30) as compared to patients that survive more than a year (1.46 x 10 ^-3 mm ²/sec, 95%CI 1.19, 1.67, p=0.057).

CONCLUSION

Analysis of diffusion characteristics in diffuse midline gliomas originating in the thalamus and pons did not identify a difference in ADC histogram parameters based on presence of histone H3 K27M mutation. However, patients with shorter survival exhibit reduced diffusion within the tumor as compared to longer survivors.

CLINICAL RELEVANCE

Diffusion characteristics of pediatric diffuse gliomas identify a subgroup of patients with lower diffusivity that corresponds to lower overall survival at one year after diagnosis, while showing no difference in diffusion characteristics between histone H3 K27M mutant and wildtype midline tumors.