DENVER – The PCA3 urine test may improve early detection of prostate cancer, especially in African Americans, who have the highest risk for the disease of any racial group, investigators reported here at the American Association for Cancer Research Annual Meeting.
The PCA3 test is performed on prostate cells loosened during a digital rectal examination (DRE) and then washed out by urine. The assay is designed to detect a certain gene that is highly overexpressed in prostate cancer cells.
“For clinical use, I certainly see this test as an important new test,” said lead investigator Adrie van Bokhoven, PhD, Assistant Professor of Pathology at the University of Colorado at Denver. The PCA3 test is increasingly being used in clinical practice, but its feasibility and performance have not been evaluated in a true screening population, Dr. van Bokhoven noted.
He and his colleagues evaluated the PCA3 test in a community-based screening population over a three-year period (2006-2008) during Prostate Cancer Awareness Week. A varied group of clinicians received instructions on the extended DRE required to release prostate cells, which are collected in the first-catch urine.
All samples were processed within one to four hours and frozen at -80ºC. PCA3 results were generated for 349 men in 2006, 311 men in 2007, and 455 men in 2008. In 2006, 2007, and 2008, subjects were 71%, 73%, and 78% white, 17%, 18%, and 13% African American, and 9%, 7%, and 7% Hispanic, respectively.
The positive rate for PCA3 (a score of 35 or higher) was 25% for white men in 2006 and 2007 and 26% in 2008. For African-American men, the positive rate was 42% in 2006, 35% in 2007, and 22% in 2008. The positive rate was much lower for Hispanics (16%, 17%, and 18%, respectively). The informative rate (the proportion of test results that were valid) was 98.6% in 2006, 96.8% in 2007, and 99.5% in 2008.
The proportion of subjects having both PCA3-positive and PSA-positive tests (2.5 ng/mL or greater) was lower in Hispanic men (0%-6% during the three years) compared with white men (9%-11%) and African-American men (4%-12%). However, the proportion of subjects having a positive PCA3 test and negative PSA test was higher in African Americans (18%-30%) than whites (15%-16%) and Hispanics (10%-18%).
“The PCA3 assay is acceptable to men and can be performed in a busy screening setting. The excellent informative rate shows the robustness of this test,” the researchers concluded in a poster displaying their findings.
In an interview with Renal & Urology News, Dr. van Bokhoven observed: “PSA is certainly not a perfect screening tool for prostate cancer, and we are hoping that this marker can add [to the information we get with PSA] or replace some of the difficulties we have with it. There is also the hope that PCA3 can help identify the more aggressive cancers, which is actually what an ideal marker would do. Finding more prostate cancers is not the goal; finding aggressive cancers that need treatment is the goal.”
The test can cost between $200 and $300 and requires an extended DRE, factors that could be barriers to its widespread use, Dr. van Bokhoven said. However, the PCA3 test could be particularly useful in the early detection of aggressive prostate cancer in African-American men and might reduce the number of unnecessary biopsies.