Therapeutic efficacy as predicted by quantitative assessment of murine RIF-1 tumour pH and phosphorous metabolite response during hyperthermia: an in vivo 31P NMR study

Described herein are the initial findings from an ‘in-magnet’ ³¹P NMR compatible hyperthermia system capable of concurrently heating and monitoring the metabolic response of murine tumours; the murine radiation induced fibrosarcoma (RIF-1) was employed for these studies. At thermal doses sufficient to raise tumour temperature to 41.5 and 43°C for a period of 30?min, a marked and rapid decrease in nucleoside triphosphate concentration and in pH was observed during the heating period, while inorganic phosphate concentration increased significantly but more gradually. These ³¹P NMR determined metabolic indices remained depressed/elevated throughout a 1.5?h post-hyperthermia monitoring period. Importantly, these metabolic indices correlated significantly with specific growth delay. This suggests a possible role for NMR spectroscopy in early assessment, and perhaps control, of therapeutic response to hyperthermia.