Prognostic radiology: Quantitative assessment of tumor oxygen dynamics by MRI

It is generally recognized that tumor hypoxia has a strong influence over t herapeutic outcome in the clinic. The authors have developed an oximetry ap proach using F-19 echo planar magnetic resonance imaging-FREDOM (Fluorocarb on Relaxometry using Echoplanar imaging for Dynamic Oxygen Mapping), which reveals dynamic changes based on sequential maps of regional tumor Po-2. Pr eclinical investigations focused on diverse sublimes of the Dunning prostat e R3327 tumor. As expected, intratumoral heterogeneity was considerable. Ho wever, large tumors (>3.5 cm(3)) were significantly less well oxygenated th an smaller tumors (<2 cm(3)). Faster growing, less differentiated tumors we re less well oxygenated than size-matched tumors of slower growing sublines . The greatest potential of this technique is the ability to follow the fat e of individual tumor regions with respect to interventions. For each subli ne, there was a significant response to respiratory challenge with oxygen f or initially well-oxygenated regions (baseline Po-2 > 10 mm Hg). More inter estingly, subline dependent behavior was found for initially hypoxic region s that correlated with rate of growth. The authors believe the FREDOM appro ach is essentially ripe for translation to the clinic. This approach could help to identify patients with hypoxic tumors and indicate tile feasibility of manipulating tumor characteristics through adjuvant interventions to im prove therapeutic response.