Detectability of low and intermediate or high risk prostate cancer with combined T2-weighted and diffusion-weighted MRI

Objectives To evaluate the incremental value of diffusionweighted imaging (DWI) in combination with T2-weighted imaging to detect low (Gleason score, = 6) and intermediate or high risk (Gleason score, = 7) prostate cancer. Methods Fifty-one patients who underwent MRI before prostatectomy were evaluated. Two readers independently scored the probability of tumour in eight regions of prostate on T2-weighted images (T2WI) and T2WI combined with apparent diffusion coefficient (ADC) maps. Data were divided into two groups-low risk and intermediate or high risk prostate cancer-and correlated with histopathological results. Diagnostic performance parameters, areas under the receiver-operating characteristic curve (AUCs) and interreader agreement were calculated. Results For both readers, AUCs of combined T2WI and ADC maps were greater than those of T2WI in intermediate or high risk (reader 1, 0.887 vs. 0.859; reader 2, 0.732 vs 0.662, P<0.05) prostate cancers, but not in low risk (reader 1, 0.719 vs 0.725; reader 2, 0.685 vs. 0.680, P>0.05) prostate cancers. Weighted ? value of combined T2WI and ADC maps was 0.689. Conclusions The addition of DWI to T2-weighted imaging improves the accuracy of detecting intermediate or high risk prostate cancers, but not for low risk prostate cancer detection. Key Points ̇ Gleason scores influence diagnostic performance of MRI for prostate cancer detection. ̇ Addition of DWI does not improve low risk prostate cancer detection. ̇ Combined T2WI and DWI may help select intermediate or high risk patients.