We analyzed
tumor growth delay in experimental
tumors after
hyperthermia alone,
hydralazine (HDZ) injection alone and the combination of these modalities. We also analyzed the energy parameter (
ATP/Pi ratio) obtained by 31P-MRS (magnetic resonance spectroscopy). The purpose of this study was to evaluate the usefulness of 31P-MRS as an index of anti-
tumor effect. FM3A
tumor cells were transplanted subcutaneously in the hind legs of C3H/He mice. We dipped the
tumors into a heated circulating water bath. 31P-MRS was performed with a CSI spectrometer. The anti-
tumor effect obtained with HDZ alone was insignificant, but combined treatment with
hyperthermia and HDZ had a significant synergistic effect. The
ATP/Pi ratios for all groups treated separately with HDZ or
hyperthermia were not different from the control, but the
ATP/Pi ratio decreased after combined use of these agents. There was a significant correlation between the decrease in
ATP/Pi ratio and
tumor growth delay. We observed a direct relation between the delay in
tumor growth and the decline in
ATP/Pi ratio after combined treatment with HDZ and
hyperthermia. The
ATP/Pi ratio 24 hr
after treatment may be useful in predicting the efficacy of the combined use of HDZ and
hyperthermia.