Comparing oxygen-sensitive MRI (BOLD R2*) with oxygen electrode measurements:A pilot study in men with prostate cancer

Abstract

Purpose: To explore the relationship between oxygen-sensitive Magnetic Resonance Imaging (MRI) and oxygen measurements in prostate cancer. Methods: Nine men underwent MRI examinations followed by needle oxygen measurements of tumor bearing region within prostate gland and five men further consented to biopsy. Median pO2 and hypoxic fraction &lt;5mm Hg (HP5) were derived. Biopsies were immunostained for Carbonic Anhydrase IX (CA IX), Hypoxia Inducible Factor-1 (HIF 1) and Glucose Transporter-1 (GLUT 1). Corresponding Regions-of-Interest (ROI) were delineated on T2-weighted (T2w) MRI by two observers. Median R2* was calculated for each ROI. Spearman correlation was calculated between R2* and HP5/pO2. Results: MRI quality evaluation resulted in exclusion of 4/18 ROI due to motion (n=2) and rectal air susceptibility artifact (n=2). Quality of remaining data was validated by concordance of R2* with T2w, indices and with secondary observer R2* (r=0.94, p=0.005). Correlation was observed between R2* and HP5 (r=0.76, p=0.02) and a trend was noted between R2* and pO2 (r=-0.66, p=0.07). GLUT 1 and HIF 1 were expressed in all patients, and CA IX was expressed in one patient with high HP5 (77%) and low pO2 (1.4mm Hg). Conclusions: MRI using R2* quantification is a promising tool for non-invasive imaging of prostate cancer hypoxia.</p