Determination of the cutoff level of apparent diffusion coefficient values for detection of prostate cancer.

Purpose: The aim of this study was to determine the cutoff level of apparent diffusion coefficient (ADC) values for diagnosing prostate cancer.

Materials And Methods: A total of 45 consecutive patients with prostate cancer who underwent diffusion-weighted magnetic resonance imaging (MRI) with ADC maps before radical prostatectomy were included in this retrospective study. MRI findings were correlated retrospectively with histopathological results of surgical specimens. Comparisons of ADC values between cancer and noncancer areas were performed with the two-tailed unequal variance t-test. The cutoff ADC level was determined in a way to achieve the best accuracy for detecting prostate cancer.

Results: The mean ADC value of all the cancer lesions (n =60) was 1.04 ± 0.31 (×10(-3) mm(2)/s). In the peripheral zone, the mean ADC values of cancer lesions and noncancer areas were 1.07 ± 0.35 and 1.94 ± 0.31, respectively (P < 0.001). In the transition zone, the mean ADC values of cancer lesions and noncancer areas were 1.00 ± 0.22 and 1.56 ± 0.14, respectively (P<0.001). The cutoff level for the ADC value was determined to be 1.35×10(-3) mm(2)/s. It provided sensitivity, specificity, and accuracy of 88%, 96%, and 93%, respectively.

Conclusion: The cutoff ADC level determined on the basis of the results obtained from radical prostatectomy specimens can help differentiate malignant from nonmalignant lesions.