Apparent diffusion coefficient: prostate cancer versus noncancerous tissue according to anatomical region

PURPOSE: To evaluate diagnostic performance of apparent diffusion coefficient (ADC) in differentiating prostate cancer from noncancerous tissue according to anatomical region. MATERIALS AND METHODS: In 47 patients with diffusion-weighted-MR (b-value, 0 and 1000 sec/mm2) on a 1.5 T unit, ADCs were measured in prostate cancer and in three noncancerous tissues (transitional zone, peripheral zone, and prostatic base). Diagnostic performance of ADC for differentiating cancer from noncancerous tissue was evaluated using receiver-operating-characteristics (ROC) analysis. RESULTS: Mean ADC of prostate cancer (0.963x10(-3) mm2/s) was lower than those of all noncancerous tissues (P<0.001). In noncancerous tissue, ADC differed according to anatomical region (peripheral zone, 1.572x10(-3) mm2/sec; transitional zone, 1.441x10(-3) mm2/sec; prostatic base, 1.146x10(-3) mm2/sec) (P<0.01). ADC was lower in prostate cancer than in all noncancerous tissues in 34 (72%) patients. Area under the ROC curve for differentiating cancer from noncancerous tissue in prostatic base (0.725) was less than those for differentiating cancer from noncancerous tissue in peripheral (0.952) and transitional zones (0.906) (P<0.05). Sensitivity differed according to anatomical region (peripheral zone, 98%; transitional zone, 82%; prostatic base, 66%) (P<0.05). CONCLUSION: Variable ADC in noncancerous tissue according to anatomical region may limit diagnostic performance of ADC for cancer detection.