Objectives: To evaluate the incremental value of diffusion-weighted 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 κ 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.