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

Warren Foltz¹, Andy Wu¹, Masoom Haider^2,3, Peter Chung¹, Andrew Bayley¹, Charles Catton¹, Cynthia Mnard¹

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.