Pre-treatment hyperpolarized 13C-lactate to 13C-bicarbonate ratio predicts response of brain metastases to stereotactic radiosurgery

Brain metastases are increasingly being treated with stereotactic radiosurgery; however, 20-30% of treated tumors locally recure post treatment. Hyperpolarized 1-13Cpyruvate magnetic resonance imaging (HP 13C MRI) is an emerging metabolic imaging modality that measures key metabolic phenotypes indicative of aggressive tumor phenotypes. Here we show that the pre-treatment tumor 13C-lactate to 13C-bicarbonate ratio – a marker of glycolysis and (indirectly) oxidative phosphorylation – measured via HP 1-13Cpyruvate MRI is a robust predictor of local recurrence (AUCROC=0.95, p=0.0008; AUCPRC=0.92) and can inform treatment decisions should the model predict a non-response to SRS.