The PCA3 urine test may help guide decisions about the need for repeat prostate biopsy in men with a negative initial biopsy but elevated PSA. These results were presented at the 2010 ASCO Genitourinary Cancer Symposium.

Since the late 1980s, the primary screening tool for early detection of prostate cancer has been the prostate specific antigen (PSA) test. While this test is widely used, it remains controversial, due to both false positive and false negative test results. Produced by cells in the prostate, PSA levels in the blood tend to be elevated in men who have prostate cancer. However, not all men with prostate cancer have elevated PSA, and not all men with elevated PSA have prostate cancer. PSA levels can also become elevated as a result of noncancerous conditions of the prostate.

Men who have elevated levels of PSA are often referred for a prostate biopsy in order to determine whether prostate cancer is present. Men who have a negative first biopsy, however, are often likely to remain uncertain about their risk of prostate cancer. This is because a biopsy only samples small areas of the prostate, and it’s not uncommon for a repeat biopsy to detect cancer that was missed by the first biopsy.

PCA3 is a test that could potentially help guide decisions about the need for repeat prostate biopsy in men suspected of having prostate cancer. PCA3 (prostate cancer gene 3) is overexpressed in men with prostate cancer but not in men with noncancerous prostate problems. The PCA3 test measures PCA3 expression in a sample of urine.

In the study presented at the Genitourinary Cancers Symposium, the PCA3 test was evaluated in 1,072 men who had PSA levels between 2.5 and 10 ng/mL and a negative initial biopsy. Repeat biopsies were performed after the second and fourth year of the study.

• A higher PCA3 result indicated a greater likelihood of finding prostate cancer on a repeat prostate biopsy. Prostate cancer was diagnosed in only 6% of men with a low PCA3 score but in 57% of men with a high PCA3 score.
• PCA3 results were correlated with cancer aggressiveness: men with high-grade cancers tended to have higher PCA3 results than men with low-grade cancer.
• PCA3 results also provided information about the likelihood of a future positive biopsy: men who had high PCA3 but a negative prostate biopsy at the two-year mark were more than twice as likely to have prostate cancer detected at the four-year mark than men with low PCA3.

These results suggest that the PCA3 test provides useful information about the need for repeat prostate biopsy in men with elevated PSA.

Reference: Groskopf J, Aubin SM, Reid J et al. Validation of the PCA3 molecular urine test for predicting repeat prostate biopsy outcome in the placebo arm of the dutasteride REDUCE trial. Presented at the ASCO 2010 Genitourinary Cancers Symposium. March 5-7, 2010. San Francisco, CA. Abstract 5.