Prostate cancer: Contrast-enhanced US for detection

PURPOSE: To assess the detection of prostate cancer with contrast material-enhanced transrectal sonography. MATERIALS AND METHODS: Sixty subjects were examined with conventional gray-scale, harmonic gray-scale, and power Doppler sonography. Evaluation was repeated during intravenous infusion of contrast agent. Gray-scale imaging was performed in continuous mode and with intermittent imaging by using interscan delay times of 0.5, 1.0, 2.0, and 5.0 seconds. Sextant biopsy sites were scored prospectively as benign or malignant at baseline imaging and again during enhanced transrectal sonography. RESULTS: Prostate cancer was present in 37 biopsy sites from 20 subjects. Baseline imaging demonstrated prostate cancer in 14 sites in 11 subjects. Enhanced transrectal sonography depicted prostate cancer in 24 sites in 15 subjects. Each of the five subjects in whom prostate cancer was missed had only a single biopsy core with positive findings (Gleason score less than or equal to 6). In three of these five subjects, prostate cancer made up less than 10% of the core. The improvement in sensitivity from 38% (14 of 37 malignant foci) at baseline to 65% (24 of 37 malignant foci) with contrast enhancement was significant (P <.004, McNemar <chi>(2) test). Specificity was similar at baseline (267 [83%] of 323 malignant foci) and during enhanced transrectal sonography (257 [80%] of 323 malignant foci). Clustered receiver operating characteristic analysis demonstrated significant improvement in diagnostic accuracy during enhanced transrectal sonography (P=.027). CONCLUSION: Enhanced transrectal sonography improves sensitivity for the detection of malignant foci within the prostate without substantial loss of specificity. Low-volume tumors with a Gleason score of 6 or less may not be detected with enhanced transrectal sonography.