A prospective sub-analysis conducted as part of a large prostate cancer prevention trial (REDUCE) finds that the PCA3 urine test accurately predicts whether a prostate biopsy will reveal cancer. The results confirm and expand on previous studies indicating that the PCA3 test can be used as another tool to determine how frequently prostate cancer biopsies are needed in men suspected to have prostate cancer.

"The addition of the PCA3 urine test to routine PSA testing significantly improves the ability to accurately diagnose prostate cancer," said lead author Jack Groskopf, PhD, Director of Research and Development in Cancer Diagnostics at Gen-Probe Incorporated, the manufacturer of the PCA3 test. "This study confirms that the PCA3 test can help physicians determine whether repeat prostate biopsy is needed among men with an elevated PSA test."

Men who have an elevated PSA test may need to have a biopsy of the prostate to see if they have prostate cancer. If the biopsy is negative and PSA remains elevated, they may undergo repeat biopsies periodically, subjecting them to an invasive procedure that is occasionally associated with complications such as infection.

PCA3 (prostate cancer gene 3) is a gene that is overexpressed in prostate cancer, but not in benign prostate disorders such as prostatitis or enlarged prostate (disorders which can also elevate PSA). The PCA3 molecular test measures PCA3 expression in urine samples. It has been validated in previous smaller studies. The test marketed in Europe as PROGENSA PCA3, and is available in certain certified laboratories in the United States as an "LDT" (laboratory developed test). The manufacturer is currently enrolling subjects in a separate clinical trial under U.S. Food and Drug Administration (FDA) guidance, a required step before the test can be submitted for FDA approval, expected later this year.

In the largest study to date to examine the PCA3 test, the researchers evaluated the test among 1,072 men who were in the placebo arm of the REDUCE Trial. The primary goal of the four-year REDUCE Trial was to determine if the drug dutasteride reduces prostate cancer risk. The current analysis was performed on patients in the REDUCE trial because all men in the placebo arm were already scheduled to undergo regular biopsies at two and four years into the study.

Researchers found that PCA3 score was significantly correlated with a positive prostate biopsy result, and that men who had higher PCA3 scores were more likely to have prostate cancer: cancer was diagnosed in only 6 percent of men with a PCA3 score below 5, but in 57 percent of men with a PCA3 score over 100. PCA3 scores also correlated with cancer aggressiveness: median PCA3 scores were higher in men with high-grade cancers than in those with low-grade cancers. The PCA3 test also predicted the likelihood of having prostate cancer diagnosed on a future biopsy: men with elevated PCA3 scores and a negative biopsy at the two-year mark were twice as likely as men with lower PCA3 scores to have cancer detected through prostate biopsy at the four-year mark.


Source: ASCO