OBJECTIVE: The purpose of our study was to identify low-risk prostate cancer on the basis of the D'Amico clinical risk score in patients with prostate-specific antigen (PSA) levels 10 ng/mL or less who had undergone radical prostatectomy by comparing apparent diffusion coefficient (ADC) with transrectal ultrasound (TRUS)-guided target biopsy. MATERIALS AND METHODS: In the preliminary study, we used receiver operating characteristic (ROC) analysis and determined the cutoff ADC to identify prostate cancer with a Gleason score of 6 or less for 117 patients. In the primary study, we assessed the combination of routine MRI (T2-weighted and diffusion-weighted imaging) plus the cutoff ADC value ("method A") to identify low-risk prostate cancer for another 89 patients. Their diagnostic value was compared with that of routine MRI combined with the Gleason score obtained from TRUS-guided target biopsies ("method B"). RESULTS: The preliminary study showed that a mean ADC of 1.04 × 10(-3) mm(2)/s was the best cutoff. In the primary study, accuracy was statistically higher with method A for each reader (p = 0.041). CONCLUSION: In patients with PSA levels 10 ng/mL or less, the combination of MRI findings plus the cutoff ADC is significantly more accurate for the identification of low-risk prostate cancer than is the combination of MRI followed by TRUS-guided target biopsy.
OBJECTIVE: The purpose of our study was to identify low-risk prostate cancer on the basis of the D'Amico clinical risk score in patients with prostate-specific antigen (PSA) levels 10 ng/mL or less who had undergone radical prostatectomy by comparing apparent diffusion coefficient (ADC) with transrectal ultrasound (TRUS)-guided target biopsy. MATERIALS AND METHODS: In the preliminary study, we used receiver operating characteristic (ROC) analysis and determined the cutoff ADC to identify prostate cancer with a Gleason score of 6 or less for 117 patients. In the primary study, we assessed the combination of routine MRI (T2-weighted and diffusion-weighted imaging) plus the cutoff ADC value ("method A") to identify low-risk prostate cancer for another 89 patients. Their diagnostic value was compared with that of routine MRI combined with the Gleason score obtained from TRUS-guided target biopsies ("method B"). RESULTS: The preliminary study showed that a mean ADC of 1.04 × 10(-3) mm(2)/s was the best cutoff. In the primary study, accuracy was statistically higher with method A for each reader (p = 0.041). CONCLUSION: In patients with PSA levels 10 ng/mL or less, the combination of MRI findings plus the cutoff ADC is significantly more accurate for the identification of low-risk prostate cancer than is the combination of MRI followed by TRUS-guided target biopsy.