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Abstract #4261

Changes in Dynamic Contrast Enhanced MRI Paramters in the First 8 Weeks of Prostate Radiotherapy

Masoom A. Haider1, Peter Chung2, Warren Foltz2, Anna Kirilova2, Charles Catton2, Padraig Warde2, Andrew Bayley2, Robert Bristow2, Michael Milosevic2, Cynthia Menard2

1Medical Imaging, University of Toronto, Princess Margaret Hospital, Toronto, Ontario, Canada; 2Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario, Canada

Twelve patients underwent DCE MRI of the prostate prior and at 2, 4, 6, and 8 weeks during external bean radiotherapy. There was a significant moderate positive correlation between cumulative radiation dose and percent change in Ktrans, ve, and IAUCC60 for the whole prostate, peripheral zone and transition zone (0.53-0.69, p<0.0005). The overall pattern consisted of a maximal two week incremental increase occurring in the first 4 weeks during therapy. The 2-4 week period during the course of radiotherapy may be the best time to assess the potential prognostic value of DCE MRI.