IMAGING

Prostate: high-frequency Doppler US imaging for cancer detection
Halpern EJ, Frauscher F, Strup SE, Nazarian LN, O’Kane P, Gomella LG
Departments of Radiology and Urology, Jefferson Prostate Diagnostic Center, Thomas Jefferson University, Philadelphia, PA, USA
Radiology 2002; 225:71-77

• Purpose: To evaluate cancer detection with targeted biopsy of the prostate performed on the basis of high-frequency Doppler ultrasonographic (US) imaging findings versus cancer detection with a modified sextant biopsy approach with laterally directed cores.
• Materials and Methods: Sixty-two patients were prospectively evaluated with gray-scale, color, and power Doppler transrectal US performed with patients in the lithotomy position. Gray-scale and Doppler findings within each sextant were rated on a five-point scale. Up to four targeted biopsy specimens were obtained from each patient on the basis of Doppler findings; this was followed by a modified sextant biopsy. Conditional logistic regression analysis was performed to compare the positive yields for targeted and sextant biopsy specimens. Clustered receiver operating characteristic analysis was performed to compare gray-scale, color, and power Doppler detection of cancer at sextant biopsy sites.
• Results: Cancer was detected in 18 (29%) of 62 patients, including 11 patients in whom cancer was detected with both sextant and targeted biopsy, six in whom cancer was detected only with sextant biopsy, and one in whom cancer was detected only with targeted biopsy. The positive biopsy rate for targeted biopsy (24 [13%] of 185 cores) was slightly higher than that for sextant biopsy (36 [9.7%] of 372 cores; P = .1). The odds ratio for cancer detection with targeted versus sextant cores was 1.8 (95% CI: 0.9, 3.7). Receiver operating characteristic analysis demonstrated that overall identification of positive sextant biopsy sites was close to random chance for gray-scale (area under the curve, 0.53), color Doppler (area under the curve, 0.50), and power Doppler (area under the curve, 0.47) imaging.
• Conclusion: Targeted biopsy performed on the basis of high-frequency color or power Doppler findings will miss a substantial number of cancers detected with sextant biopsy.
  
  
• Editorial Comment
  Eighty-five percent of prostate cancers appear with variable degree of increased flow when evaluated by color and power Doppler sonography. For this reason, power Doppler has been used routinely as a complimentary tool during transrectal US-guided biopsy of the prostate. Color Doppler ultrasound is able to demonstrate 10-15% of cancers only by their hypervascularity, since such lesions appear isoechoic in the normal peripheral zone on gray-scale technique (1-3).
  This study was performed in order to evaluate the detection of prostate cancer by targeted biopsy guided by the findings of high-frequency color and power Doppler techniques compared to modified sextant biopsy scheme. The authors concluded that targeted biopsy guided only by the findings of color and power Doppler US will miss a substantial number of cancers. Few points, however, should be considered regarding their results and conclusions. First, we should not consider any focal area of increased flow suspicious for cancer. Conversely, an area highly suspicious for cancer is the one presenting a “chaotic” flow. “Chaotic” flow is represented by a cluster of irregular and tortuous vessels. The authors did not attempt to differentiate these patterns of hypervascularity. Secondly, power Doppler, particularly when associated with intravenous injection of echo-contrast, is useful as a complimentary tool for a modified sextant biopsy scheme. After the administration of echo-contrast, the sensitivity of power Doppler in detecting cancer increases from 38% to 85% (3). In our department, we perform a modified sextant biopsy scheme (12 cores from the peripheral zone), plus 2 cores from any abnormal finding in prostate texture, and plus 2 cores of any area with abnormal flow. This protocol has been shown to be of value, particularly in patients with large prostates (above 100 cm3). In conclusion, targeted biopsy performed only on the basis of power Doppler US technique continues to be insufficient to diagnose prostate cancer.

References
1. Lavoipierre AM, Snow RM, Frydenberg M, et al.: Prostate cancer: role of Doppler imaging in TRUS. AJR 1998; 171:205-210.
2. Newman JS, Bree RL, Rubin JM: Prostate cancer: diagnosis with color Doppler sonography with histologic correlation of each biopsy site. Radiology 1995; 195:86-90.
3. Bogers HA, Sedelaar JP, Beerlage HP, et al.: Contrast-enhanced 3-D power Doppler angiography of the human prostate: correlation with biopsy outcome. Urology 1999; 54:97-104.

Dr. Adilson Prando
Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil