Monitoring of tumor reoxygenation following irradiation by P-31 magnetic resonance spectroscopy: an experimental study of human melanoma xenografts

Background and purpose: Inadequate tumor reoxygenation during radiation the rapy may cause local treatment failure. This study was aimed at investigati ng the potential usefulness of P-31-MRS in monitoring tumor reoxygenation f ollowing radiation treatment. Materials and methods: Tumors of two human melanoma xenograft lines (BEX-t and HUX-t) were exposed to 15.0 Gy, and then the fraction of radiobiologica lly hypoxic cells, measured by using the paired survival curve method, or t umor bioenergetic status, measured by P-31-MRS as the (PCr + NTP beta)/P-i resonance ratio, was determined versus time after the radiation exposure. Results: Untreated BEX-t and HUX-t tumors showed similar fractions of radio biologically hypoxic cells and similar bioenergetic status, whereas both pa rameters differed substantially between the lines in irradiated tumors. A c lose association was found between radiation-induced changes in tumor bioen ergetic status and radiation-induced changes in the fraction of radiobiolog ically hypoxic cells. Conclusion: P-31-MRS is a potentially useful method for monitoring tumor re oxygenation following radiation treatment. (C) 1999 Elsevier Science irelan d Ltd. All rights reserved.