Follow-up by 31P NMR spectroscopy of the energy metabolism of malignant tumor in rats during treatment.

The energy metabolism of tumors in rats was investigated by in vivo 31P-NMR spectroscopy. The effects of radiotherapy, chemotherapy or radiotherapy combined with 5-fluorouracil (5-FU) chemotherapy were evaluated by observing the changes of these spectra in chemically induced subcutaneous fibrosarcoma in rats. Two milligrams of DMBA in solution in olive oil were administered subcutaneously in the flank of 20 Wistar rats and 17 fibrosarcoma occurred. 31P NMR spectra were recorded with a Brüker Medspec 30/47 spectrometer using a surface coil positioned over the tumor. We did not observe significant changes in the spectra during tumor growth. Radiotherapy and 5-FU chemotherapy alone did not induce major changes in the 31P spectra. But the situation was completely different for animals receiving the therapeutic combination. A clear increase in the ratio of inorganic phosphate to total phosphorus signal was observed 48 h after the first irradiation session. The pH shifted concurrently to the acidic range. No effect on tumor regression was observed in the rats from the chemotherapy group, while regression was less than 50% in rats treated by irradiation only, and at least 80% in the combined group.