Correlating quantitative MR measurements of standardized tumor lines with histological parameters and tumor control dose

Purpose: To correlate non-invasively acquired radiobiologically relevant magnetic resonance (MR) parameters with functional histology and tumor control doses (TCD(50)). Materials and methods: The MR parameters relative perfusion, re-oxygenation and lactate (Lac) concentration from eight human xenograft squamous tumor lines were compared with the histologically acquired pimonidazole hypoxic fraction, the perfused vessel area and TCD(50). Results: Good spatial correlation in the parameter maps could be observed between the pimonidazole staining and tumor regions, which can be reoxygenated when breathing carbogen. A strong positive correlation (R = 0.74) was found between whole tumor pimonidazole hypoxic fraction and re-oxygenation, as one would expect. A good correlation was also observed between Lac concentration and re-oxygenation (R = 0.71) and between TCD(50) and re-oxygenation (R = 0.64), whereas Lac and TCD(50) showed a moderate relation (R = 0.44). The in vivo measurement of relative perfusion could be validated to reflect the perfused vessel area (R = 0.63). No correlation was detected between perfusion and re-oxygenation or TCD(50). Conclusions: Lac and re-oxygenation were shown to be pretreatment predictive markers independent from the pathophysiological changes induced during a fractionated course of radiotherapy. These parameters hold promise to be acquired non-invasively with results just a few minutes after measurement and to tailor radiotherapy to individual patterns of a tumor microenvironment. (C) 2010 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 96 (2010) 123-130