Apparent diffusion coefficient of the prostate in men prior to biopsy: determination of a cut-off value to predict malignancy of the peripheral zone

Determination of the apparent diffusion coefficient (ADC) of the prostate in men (n = 60) with raised prostate‐specific antigen (PSA) or an abnormal digital rectal examination (DRE) prior to transrectal ultrasound (TRUS) guided biopsy using endorectal DWI is reported. Patients were categorized into different groups based on their PSA levels. The mean ADC was calculated from a number of regions of interest (ROIs) for the whole of the peripheral zone (PZ) and the central gland (CG). A total of 1108 ROIs were analyzed from 60 patients. The mean ADC value of the PZ was higher than that of the CG in controls. A total of 23 out of 60 patients were positive for malignancy on biopsy, and the mean ADC of the PZ was lower in these patients compared with those who were negative. Moreover, the mean ADC obtained for the whole of the PZ of the prostate in different groups of patients and controls showed a decreasing trend. A plot between PSA and mean ADC for the PZ showed non‐linear association with logarithmic decrease in ADC. The mean ADC of the CG was not significantly different in patients who were positive or negative for malignancy in biopsy. In addition, a cut‐off value of 1.17 × 10−3 mm2/s (sensitivity = 73% and specificity = 74%, area under the curve = 0.83) for the mean ADC for the whole of the PZ of patients was determined by using the receiver operating characteristic curve (ROC) to predict malignancy of the PZ. Copyright © 2006 John Wiley & Sons, Ltd.