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Effect of Tamoxifen in an Experimental Model of Breast Tumor Studied by Dynamic Contrast-Enhanced Magnetic Resonance Imaging and Different Contrast Agents

Objectives:The aim of this study was to compare the efficacy of gadoteridol, B22956/1 (a new protein binding blood pool contrast agent), and (Gd-DTPA)37-albumin in detecting, by dynamic contrast-enhanced magnetic resonance imaging (MRI), the effect in vivo of tamoxifen in an experimental model of breast tumor implanted in rats. Materials and Methods:Tumors were induced by subcutaneous injection of 106 mammary adenocarcinoma cells (13762 MAT B III). Treatment with tamoxifen (or vehicle) started on day 4 after implantation. On day 10 after implantation, animals were observed by MRI using B22956/1 (or gadoteridol) and, 24 hours later, using (Gd-DTPA)37–albumin. Results:Dynamic contrast-enhanced magnetic resonance imaging data showed that tamoxifen treatment decreased vascular permeability to B22956/1, whereas no difference was detectable in permeability to gadoteridol or to (Gd-DTPA)37–albumin. No effect on fractional plasma volume was detected with either of contrast agents. Conclusions:B22956/1 is superior to both small Gd chelates and macromolecular contrast agents in the assessment of the effect of tamoxifen treatment on tumor vasculature.