Dynamic contrast-enhanced magnetic resonance imaging of osseous spine metastasis before and 1 hour after high-dose image-guided radiation therapy

OBJECTIVE High-dose image-guided radiation therapy (HD IGRT) has been instrumental in mitigating some limitations of conventional RT. The recent emergence of dynamic contrast-enhanced (DCE) MRI to investigate tumor physiology can be used to verify the response of human tumors to HD IGRT. The purpose of this study was to evaluate the nearimmediate effects of HD IGRT on spine metastases through the use of DCE MRI perfusion studies. METHODS Six patients with spine metastases from prostate, thyroid, and renal cell carcinoma who underwent HD IGRT were studied using DCE MRI prior to and 1 hour after HD IGRT. The DCE perfusion parameters plasma volume (V-p) and vascular permeability (K-trans) were measured to assess the near-immediate and long-term tumor response. A Mann-Whitney U-test was performed to compare significant changes (at p <= 0.05) in perfusion parameters before and after RT. RESULTS The authors observed a precipitous drop in V-p within 1 hour of HD IGRT, with a mean decrease of 65.2%. A significant difference was found between V-p values for before and 1 hour after RT (p <= 0.05). No significant change was seen in V-p (p = 0.31) and K-trans (p = 0.1) from 1 hour after RT to the first follow-up. CONCLUSIONS The data suggest that there is an immediate effect of HD IGRT on the vascularity of spine metastases, as demonstrated by a precipitous decrease in V-p. The DCE MRI studies can detect such changes within 1 hour after RT, and findings are concordant with existing animal models.