Tumor growth kinetics of low-risk prostate cancer in 15 men managed by active surveillance with size increase on repeat MRI were correlated with ADC histogram metrics. Measurements were made over 3 time-points at least 1 year apart (mean 3.6 ± 0.95 years). Median growth was 23.1% in the first interval and 49.8% in the second. ADC reduced over time. Accelerated growth during the second time interval correlated with the increase in interquartile range (r=0.6, p=0.02) and shift to more positive skew (r=-0.56, p=0.03) seen during the first time interval, suggesting that increasing heterogeneity and reducing ADC may signal accelerated growth.