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Abstract #2717

Apparent Diffusion Coefficient as an Early Quantitative Biomarker of Radiation Response in Prostate Cancer

Warren Foltz1, Andy Wu1, Masoom Haider2,3, Peter Chung1, Andrew Bayley1, Charles Catton1, Cynthia Mnard1

1Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario, Canada; 2Medical Imaging, University Health Network, Toronto, Ontario, Canada; 3Medical Imaging, University of Toronto

Apparent diffusion coefficent (ADC) increases with cytoxic interventions, and may provide an early response biomarker for prostate radiotherapy. This study evaluated prostate zonal and tumor ADC using clinically normal and high b-values in low/intermediate risk patients at baseline and at 2-week intervals throughout their 8-week radiation treatment. Central gland ADC elevated moderately but significantly throughout treatment, while uninvolved peripheral zone ADC trended towards a late reduction. Tumor ADC was elevated in all follow-up scans, to 15% at week 8. SNR analysis at each b-value identified the minimum region volume for noise-insensitive measurements, to guide protocol design for future voxel-based assessment.