Preliminary observations on the correlation of proliferative phenomena with in vivo /sup 31/P NMR spectroscopy after tumor chemotherapy

In order to translate the concepts that have been developed in animal systems to human treatment programs, there is an urgent need for noninvasive techniques to study tumor cell biology. The characteristics of the ideal technique for the noninvasive monitoring of cell proliferation are truly imposing. The method should not require repeated biopsies; it should be amenable to repeated studies at frequent intervals without patient discomfort; it should monitor the proliferative response to the treatment modality; and it should not, in itself, perturb the tumor. Ideally, one would also like to be able to evaluate normal cell proliferation as well. It appears now that a new technique, /sup 31/P nuclear magnetic resonance (/sup 31/PNMR), may fulfill these rather rigid requirements. However, many studies in animal systems are necessary before it can be applied to the study of human tumors. The theory and mechanics of /sup 31/P NMR have been well described. Recently, its use as a noninvasive technique to study in vivo metabolic processes has become important. The authors presented a series of reports on the use of /sup 31/P NMR for the evaluation of tumor metabolism in animal systems under a variety of conditions. Studies of subcutaneously transplanted mouse tumors and human xenografts detected significant changes in nucleotide triphosphate (NTP), phosphocreatine, and inorganic phosphorus (Pi) as a result of tumor growth and perturbation with chemotherapeutic drugs, radiation, and hyperthermia. Their collabortive studies were designed to evaluate the changing effects of a noncurative single dose of cyclophosphamide on the /sup 31/P NMR resonances from the RIF-1 tumor, and to compare them with the proliferative changes that occur with time after drug administration. They were carried out in the hope of finding a noninvasive correlate with tumor cell proliferation