P-31 MAGNETIC-RESONANCE SPECTROSCOPY AFTER COMBINED HYPERTHERMIA AND RADIATION

Mechanisms of uveal melanoma response to therapy are poorly understood . There are a paucity of changes that have been detected immediately a fter tumor treatment to differentiate successful from ineffective ther apy. In this study we used in vivo P-31 magnetic resonance spectroscop y (MRS) to assess intratumor treatment alterations. The metabolic cons equences of effective and ineffective levels of solitary hyperthermia and combined hyperthermia-radiation were investigated. We have previou sly noted a characteristic P-31 MRS pattern with successful hypertherm ia in this intraocular melanoma model. The metabolic response after ef fective or ineffective combined radiation/ hyperthermia therapy was in distinguishable from solitary radiation therapy and opposite to that w ith successful hyperthermia therapy. In contrast to solitary hyperther mia therapy, early changes in P-31 spectral ratios following radiation or combined hyperthermia/ radiation therapy of uveal melanoma were no t predictive of treatment response. Twenty-four to 48 hours after effe ctive or ineffective radiation or combined treatment the Pi/beta-NTP r atio decreased significantly (Delta Pi/beta-NTP = -0.433 +/- 0.08 and -0.478 +/- .13 and .10 +/- 0.2, respectively). There was over a 2.0 th ermal enhancement of radiation with heat. The increased tumor cell dea th after combined therapy was reflected by a two-fold larger decrease in beta-NTP signal-to-noise (S/N).