A role for dynamic contrast-enhanced magnetic resonance imaging in predicting tumour radiation response

Background: Dynamic contrast-enhanced (DCE) MRI may provide prognostic insights into tumour radiation response. This study examined quantitative DCE MRI parameters in rat tumours, as potential biomarkers of tumour growth delay following single high-dose irradiation. Methods: Dunning R3327-AT1 prostate tumours were evaluated by DCE MRI following intravenous injection of Gd-DTPA. The next day tumours were irradiated (single dose of 30 Gy), while animals breathed air (n = 4) or oxygen (n = 4); two animals were nonirradiated controls. Growth was followed and tumour volume-quadrupling time (T-4) was compared with pre-irradiation DCE assessments. Results: Irradiation caused significant tumour growth delay (T-4 ranged from 28 to 48 days for air-breathing rats, and 40 to 75 days for oxygen-breathing rats) compared with the controls (T-4 = 7 to 9 days). A strong correlation was observed between T-4 and extravascular-extracellular volume fraction (ve) irrespective of the gas inhaled during irradiation. There was also a correlation between T4 and volume transfer constant (Ktrans) for the air-breathing group alone. Conclusions: The data provide rationale for expanded studies of other tumour sites, types and progressively patients, and are potentially significant, as many patients undergo contrast-enhanced MRI as part of treatment planning.