Evaluation of thermal damage after hyperthermia on murine experimental tumor by 31P-NMR spectroscopy--correlation between ATP and growth delay.

The usefulness of 31P-MRS (phosphate magnetic resonance spectroscopy) for evaluation of the anti tumor effect of hyperthermic treatment was examined. FM3A, an experimental tumor transplantable to C3H mice, was used. FM3A, transplanted subcutaneously to the femoral region, was subjected to hyperthermic treatment and 31P-MRS were measured at various times. Because the ATP/Pi ratio indicates the energy status of tumor cells, we conducted measurement of its sequential changes after hyperthermic treatment. With a water bath, hyperthermic treatment was performed at 44 degrees C. Twenty four hours after treatment, the ATP/Pi ratio dropped as the heating time was prolonged, showing an obvious converse correlation to the tumor growth curve on heating. Immediately after hyperthermic treatment, the ATP/Pi ratio fell drastically, began to recover after 18 hrs and remained unchanged up to the 24 hrs. The finding that the ATP/Pi ratio obtained in tumor tissue 24 hrs after hyperthermic treatment was correlated with tumor inhibition suggested that the ratio can be a possible parameter for evaluation of the anti tumor effect by heating. The ATP/Pi ratio obtained by 31P-MRS could be used for non-invasive prediction of tumor tissue damage by heating.