Monitoring human tumor response to therapy by means of P-31 MR spectroscopy.

Tumors in 23 patients were studied by means of in vivo phosphorus-31 magnetic resonance (MR) spectroscopy. In five patients, the response to chemotherapy and radiation therapy was monitored in a long-term follow-up study. In one patient, the P-31 MR spectra were recorded during the infusion of chemotherapeutic drugs. In comparison with healthy muscle tissue of patients, the tumors showed elevated inorganic phosphate, phosphomonoester, and phosphodiester peaks and reduced creatine phosphate peaks, whereas the nucleoside 5'-triphosphate levels remained nearly unchanged. Tumor treatment resulted in changes in the ratio of the signal intensity value of creatine phosphate to that of inorganic phosphate and in the sum of these values. In an osteosarcoma, an initial response followed by renewed tumor growth was clearly indicated by changes in these parameters. In the short-term follow-up examination, slight spectral changes were observed during the infusion of chemotherapeutic drugs. Changes in the concentrations of phosphorus metabolites during therapy can therefore be monitored in human tumors by means of P-31 MR spectroscopy.