UCSF

Background

Dynamic hyperpolarized (HP)-¹³C MRI has enabled real-time, non-invasive assessment of Warburg-related metabolic dysregulation in glioma using a [1-¹³C]pyruvate tracer that undergoes conversion to [1-¹³C]lactate and [¹³C]bicarbonate. Using a multi-parametric ¹H/HP-¹³C imaging approach, we investigated dynamic and steady-state metabolism, together with physiological parameters, in high-grade gliomas to characterize active tumor.

Methods

Multi-parametric ¹H/HP-¹³C MRI data were acquired from fifteen patients with progressive/treatment-naïve glioblastoma [prog/TN GBM, IDH-wildtype (n = 11)], progressive astrocytoma, IDH-mutant, grade 4 (G4A^IDH+, n = 2) and GBM manifesting treatment effects (n = 2). Voxel-wise regional analysis of the cohort with prog/TN GBM assessed imaging heterogeneity across contrast-enhancing/non-enhancing lesions (CEL/NEL) and normal-appearing white matter (NAWM) using a mixed effects model. To enable cross-nucleus parameter association, normalized perfusion, diffusion, and dynamic/steady-state (HP-¹³C/spectroscopic) metabolic data were collectively examined at the ¹³C resolution. Prog/TN GBM were similarly compared against progressive G4A^IDH+ and treatment effects.

Results

Regional analysis of Prog/TN GBM metabolism revealed statistically significant heterogeneity in ¹H choline-to-N-acetylaspartate index (CNI)_max, [1-¹³C]lactate, modified [1-¹³C]lactate-to-[1-¹³C]pyruvate ratio (CEL_val > NEL_val > NAWM_val); [1-¹³C]lactate-to-[¹³C]bicarbonate ratio (CEL_val > NEL_val/NAWM_val); and ¹H-lactate (CEL_val/NEL_val > NAWM_undetected). Significant associations were found between normalized perfusion (cerebral blood volume, nCBV; peak height, nPH) and levels of [1-¹³C]pyruvate and [1-¹³C]lactate, as well as between CNI_max and levels of [1-¹³C]pyruvate, [1-¹³C]lactate and modified ratio. GBM, by comparison to G4A^IDH+, displayed lower perfusion %-recovery and modeled rate constants for [1-¹³C]pyruvate-to-[1-¹³C]lactate conversion (k_PL), and higher ¹H-lactate and [1-¹³C]pyruvate levels, while having higher nCBV, %-recovery, k_PL, [1-¹³C]pyruvate-to-[1-¹³C]lactate and modified ratios relative to treatment effects.

Conclusions

GBM consistently displayed aberrant, Warburg-related metabolism and regional heterogeneity detectable by novel HP-¹³C/¹H imaging techniques.