Diffusion-Weighted Magnetic Resonance Imaging in Patients With Unilateral Prostate Cancer on Extended Prostate Biopsy: Predictive Accuracy of Laterality and Implications for Hemi-Ablative Therapy

Abstract

We evaluated the ability of extended prostate biopsy to detect unilateral prostate cancer and assessed the incremental diagnostic benefit of diffusion-weighted magnetic resonance imaging to predict unilateral prostate cancer. A total of 130 patients with prostate cancer detected by extended pattern prostate biopsy underwent magnetic resonance imaging before radical prostatectomy. Tumor laterality on extended prostate biopsy was compared with the corresponding lobe on the radical prostatectomy specimen. In patients with unilateral prostate cancer on biopsy we calculated the probability of a tumor in the contralateral lobe on magnetic resonance images and calculated area under the receiver operating characteristics curve. We compared the diagnostic accuracy of combined T2-weighted and diffusion-weighted magnetic resonance images to that of T2-weighted magnetic resonance images alone. Of the 130 patients 88 (67.7%) had unilateral disease on extended prostate biopsy. Radical prostatectomy pathology showed that 19% of these patients had unilateral disease but 81% had bilateral disease. Area under the receiver operating characteristics curve of combined diffusion-weighted and T2-weighted magnetic resonance imaging was greater than that of T2-weighted magnetic resonance imaging alone (0.814, 95% CI 0.716-0.889 vs 0.510, 95% CI 0.401-0.618). T2-weighted plus diffusion-weighted magnetic resonance imaging had significantly higher sensitivity (84.1% vs 61.9%, p = 0.003) and specificity (72.0% vs 36.0%, p = 0.004) to predict cancer in the contralateral lobe than T2-weighted magnetic resonance alone. Extended prostate biopsy cannot accurately determine prostate cancer unilaterality. Diffusion-weighted magnetic resonance combined with T2-weighted magnetic resonance imaging has an incremental diagnostic benefit to predict unilateral prostate cancer.