A new ultrasound technique involving color-enhanced Doppler imaging with microbubble contrast improves the accuracy of screening for prostate cancer, according to a recent article published in The Lancet.

The prostate is a male sex gland that is located between the bladder and the rectum. Prostate cancer is the second leading cause of cancer death in men in the United States. Prostate specific antigen (PSA) levels (a protein produced by the prostate that is elevated when cancer is present), a digital rectal exam (DRE) and transrectal ultrasound are common tests used to detect prostate cancer. If any suspicious mass is found through these tests, a patient must then undergo biopsies (the removal of a sample of tissue) to definitively determine whether cancer exists.

A new development in ultrasound involves the use of color Doppler imaging with microbubble contrast so that physicians are better able to determine the presence and exact location of a mass within the prostate. Doppler imaging can sense differences in velocity (i.e. blood flow versus solid tissue) and transmits these differences through different color pixels to create a picture on a screen. Microbubbles are tiny bubbles of gas that can permeate through small blood vessels without creating any harm. The microbubbles further enhance imaging by increasing the intensity of backscatter signal. Since blood vessels and blood flow are more prevalent in cancerous tissues than regular tissues, microbubbles tend to concentrate in the cancer, which is revealed on the created picture. This allows physicians to more accurately locate where biopsies should be taken.

Researchers recently compared the use of the contrast-enhanced Doppler ultrasonography with a microbubble contrast agent to conventionally used grey-scale ultrasonography. Eighty-four men involved in this study first underwent the Doppler ultrasonography and 5 biopsies. Patients then underwent grey-scale ultrasonography and 10 biopsies. The accuracy of the biopsies could then be compared in the same patient.

The detection rate of prostate cancer was 27% with Doppler-guided biopsies compared with 20% with conventional ultrasonography. The overall core biopsy detection rate was 13% for Doppler-guided biopsies compared with only 4.9% for conventional ultrasonography. These results indicate that Doppler-guided biopsies with microbubble contrast may enable physicians to more accurately determine the optimal location for a biopsy. This will allow fewer biopsies than conventional ultrasonography with an improved rate of cancer detection. Biopsies are associated with pain, infection, blood in the urine, and/or blood in the sperm. In addition, cost could be reduced by approximately 50%.

Patients undergoing transrectal ultrasonography may wish to speak with their physician about the risks and benefits of Doppler-guided ultrasonography with microbubble contrast or the participation in a clinical trial further evaluating this procedure. Two sources of information regarding ongoing clinical trials include comprehensive, easy-to-use listing services provided by the National Cancer Institute (cancer.gov) and eCancerTrials.com. eCancerTrials.com also provides personalized clinical trial searches on behalf of patients. (The Lancet, Vol 357, No 9271, 2001)

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