Intrinsic susceptibility biomarkers were found to successfully provide cross validation of the oxygen-enhanced MRI biomarker perfused Oxy-R when mapping tumor hypoxia in renal carcinoma, according to research published June 5 in Radiology.
The findings demonstrate how MRI scans may show whether a cancer patient is responding to treatment.
Researchers—led by James O'Connor, PhD, a senior lecturer in radiology at the University of Manchester and a radiologist at the Christie hospital in Manchester, England—found a consistent relationship to pathologic analyses in xenografts and malignant tumors.
The study included nine pre-clinical studies in 786–0-R renal cell carcinoma xenografts and clinical studies in eight patients with renal cell carcinoma.
"Longitudinal relaxation rate changes (∆R1) after 100 percent oxygen inhalation were quantified, reflecting the paramagnetic effect on tissue protons because of the presence of molecular oxygen," O'Connor et al. wrote. "Native transverse relaxation rate (R2) and oxygen-induced R2 change (∆R2) were measured, reflecting presence of deoxygenated hemoglobin molecules; median and voxel-wise values of ∆R1 were compared with values of R2 and ∆R2."
Additionally, tumor regions with dynamic contrast agent–enhanced MRI perfusion were identified from perfused oxygen enhancing and non-perfused regions, according to the researchers.
Study results included the following:
- Tumor-wise and voxel-wise ∆R1 and ∆R2 comparisons did not show correlative relationships.
- In xenografts, parcellation analysis revealed that perfused Oxy-R regions had faster native R2 and greater negative ∆R2, compared with perfused Oxy-E and nonperfused sub regions; similar findings were present in human tumors.
- Perfused Oxy-R helped identify tumor hypoxia, measured at pathologic analysis, in both xenografts and human tumors.