Contrast ultrasound could reduce unneeded prostate biopsies

March 9, 2009

A protocol involving contrast-enhanced ultrasound could better target tumors and reduce the number of unnecessary prostate biopsies, according to a pair of studies presented Sunday. One of the studies involved more than 2000 patients.

A protocol involving contrast-enhanced ultrasound could better target tumors and reduce the number of unnecessary prostate biopsies, according to a pair of studies presented Sunday. One of the studies involved more than 2000 patients.

The use of tumor vascularity was evaluated as a strategy for more precisely identifying the location of prostate tumors for biopsy. In studies from China and Austria, researchers imaged patients with contrast ultrasound and used the information to target biopsies. They found generally that contrast ultrasound provided more precise locational information than is available with unenhanced gray-scale ultrasound.

Both studies compared contrast and noncontrast gray-scale ultrasound and looked at the biopsy yield for the scans. They found sensitivity levels of greater than 80% for the contrast scans. Power Doppler can image vascularity, but the flow is too slow to be really useful, a problem that can be overcome by adding microbubble contrast, said Dr. Leo Pallwein of the Medical University of Innsbruck.

His study included results from 2008 men with elevated prostate-specific antigen levels from a screening population. It pitted gray-scale ultrasound with a systematic biopsy approach against contrast-enhanced power Doppler used to target specific areas for biopsy.

Biopsies based on the contrast scans resulted in a sensitivity of 85.2%. Biopsies based on the systematic approach under gray-scale scanning had a sensitivity of 73.3%. Looking at the population as a whole, the contrast-guided scans resulted in an average of five biopsy cores per patient with a positive yield of 10.8%. The gray-scale scans with a systematic biopsy approach resulted in 10 cores per patient with a positive yield of 4.5%.

The study from Jio Tong Universty in Shanghai included 65 patients. It compared gray-scale, power Doppler, and a contrast strategy the researchers called microflow imaging. Based on the biopsy site, sensitivity and accuracy figures were, respectively, 80% and 83.1% for contrast ultrasound, 46.9% and 76.8% for gray-scale, and 37.4% and 74.6% for power Doppler, according to Dr. Feng Hua Li.

Limitations of the contrast technique include cost (€30 to €60), training, the need for an injection, and false positives resulting from conditions such as prostatitis. Still, considering that more men are undergoing PSA testing and more biopsies are being scheduled, ways to limit the number of negative biopsies performed are worthwhile, Pallwein said.

At Innsbruck, the protocol for men with high PSAs is a contrast ultrasound scan, biopsy of areas of suspicion, and, if the biopsies are negative, short-term follow-up, Pallwein said.