THERAPY MONITORING IN HUMAN AND CANINE SOFT-TISSUE SARCOMAS USING MAGNETIC-RESONANCE-IMAGING AND SPECTROSCOPY

Purpose: The goals of this study were to determine whether magnetic re sonance parameters (a) can identify early during therapy those patient s most likely to respond to hyperthermia and radiotherapy, (b) can pro vide prior to or early during therapy information about the temperatur e distributions which can be obtained in patients receiving hypertherm ia, and (c) can provide an understanding of the effects of hyperthermi a on tumor metabolic status. Methods and Materials: Twenty-one human p atients and 10 canine patients with soft tissue sarcomas treated With preoperative hyperthermia and radiation had a series of magnetic reson ance imaging and phosphorus spectroscopy studies done. To address the goals for both the human and canine populations, changes in mean T-2 r elaxation times, pH, and various phosphometabolite ratios from the pre treatment (Study 1) to the post first hyperthermia study (Study 2) wer e correlated with treatment outcome; pretreatment magnetic resonance p arameters and changes in magnetic resonance parameters (Study 2-Study 1) were compared with various cumulative thermal descriptors; and ther mal descriptors of the first hyperthermia were compared with changes i n magnetic resonance phosphometabolite ratios. Results: A decrease in adenosine triphosphate/phosphomonoester from study 1 to study 2 is ass ociated,vith a greater chance of equal to or greater than 95% necrosis in surgical resected tumors from human patients, but no significant r elationships were observed between changes in tumor pH or phosphometab olite ratios and time to local failure in dogs. Pretreatment magnetic resonance parameters correlated with various thermal dose descriptors in canines but not in humans. Change in adenosine triphosphate/inorgan ic phosphate and phosphomonoester signal to noise ratio correlated wit h cumulative thermal descriptors in dogs and humans, respectively. In dogs only, increases in thermal dose resulted in decreases in high ene rgy phosphometabolites. Conclusion: Changes in magnetic resonance para meters early during therapy may be predictive of treatment outcome. Pr etreatment and changes in magnetic resonance parameters appear to pred ict how well a tumor will be heated during hyperthermia. Magnetic reso nance spectroscopy also appears to be a useful tool to study the effec ts of various thermal doses on tumor metabolic status.