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

Abstract

Inadequate tumor reoxygenation during radiation therapy may cause local treatment failure. This study was aimed at investigating the potential usefulness of 31P-MRS in monitoring tumor reoxygenation following radiation treatment. Tumors of two human melanoma xenograft lines (BEX-t and HUX-t) were exposed to 15.0 Gy, and then the fraction of radiobiologically hypoxic cells, measured by using the paired survival curve method, or tumor bioenergetic status, measured by 31P-MRS as the (PCr + NTPbeta)/Pi resonance ratio, was determined versus time after the radiation exposure. Untreated BEX-t and HUX-t tumors showed similar fractions of radiobiologically hypoxic cells and similar bioenergetic status, whereas both parameters differed substantially between the lines in irradiated tumors. A close association was found between radiation-induced changes in tumor bioenergetic status and radiation-induced changes in the fraction of radiobiologically hypoxic cells. 31P-MRS is a potentially useful method for monitoring tumor reoxygenation following radiation treatment.