Measurement of the Increase in Vessel Size Induced by a Vascular Disrupting Agent in Orthotopic Prostate Tumours Using Vessel Size Imaging

Simon Walker-Samuel¹, Jessica K. Boult¹, Lesley D. McPhail¹, Simon P. Robinson¹

In this study, susceptibility MRI with ultra-small paramagnetic iron oxide (USPIO) was used to estimate the vessel size index (VSI) in orthotopic PC3 prostate tumours following treatment with ZD6126, a vascular disrupting agent. It was found that orthotopic tumours exhibited larger vessels than typically found in ectopic (subcutaneous) tumour xenograft models (VSI = 6525m), and that this significantly increased following treatment with ZD6126 (post-treatment VSI = 12236m, p<0.05). An excellent correspondence was found with histological measurements of vessel size. This study highlights the potential use of VSI as a biomarker for assessing vascular architecture and response to vascular disrupting agents.