Measuring Tumor Metabolism in Pediatric Diffuse Intrinsic Pontine Glioma Using Hyperpolarized Carbon-13 MR Metabolic Imaging

Objective. The purpose of this study was to demonstrate the feasibility of using hyperpolarized carbon-13 (¹³C) metabolic imaging with [1-¹³C]-labeled pyruvate for evaluating real-time in vivo metabolism of orthotopic diffuse intrinsic pontine glioma (DIPG) xenografts. Materials and Methods. 3D ¹³C magnetic resonance spectroscopic imaging (MRSI) data were acquired on a 3T scanner from 8 rats that had been implanted with human-derived DIPG cells in the brainstem and 5 healthy controls, following injection of 2.5 mL (100 mM) hyperpolarized [1-¹³C]-pyruvate. Results. Anatomical images from DIPG-bearing rats characteristically exhibited T₂-hyperintensity throughout the cerebellum and pons that was not accompanied by contrast enhancement. Evaluation of real-time in vivo ¹³C spectroscopic data revealed ratios of lactate-to-pyruvate (p<0.002), lactate-to-total carbon (p<0.002), and normalized lactate (p<0.002) that were significantly higher in T₂ lesions harboring tumor relative to corresponding values of healthy normal brain. Elevated levels of lactate in lesions demonstrated a distinct metabolic profile that was associated with infiltrative, viable tumor recapitulating the histopathology of pediatric DIPG. Conclusions. Results from this study characterized pyruvate and lactate metabolism in orthotopic DIPG xenografts and suggest that hyperpolarized ¹³C MRSI may serve as a noninvasive imaging technique for in vivo monitoring of biochemical processes in patients with DIPG.