PCA3 maintains predictive value for prostate biopsy outcomes in 5-ARI users

September 1, 2010

Unlike PSA, the PCA3 assay can identify prostate biopsy outcomes even in men taking a 5-alpha-reductase inhibitor.

San Francisco-The PCA3 assay can identify prostate biopsy outcomes even in men taking a 5-alpha-reductase inhibitor, a multicenter study indicates.

Unlike serum PSA, PCA3 scores seem to be unaffected by use of dutasteride (Avodart).

"Although PCA3 has been studied in other populations, this is the first time it's been looked at in the dutasteride population," Seth Strope, MD, MPH, an assistant professor of surgery at Washington University School of Medicine in Saint Louis, told Urology Times. He presented an analysis of a subset of men in the REDUCE (Reduction by Dutasteride of Prostate Cancer Events) trial at the AUA annual meeting in San Francisco on behalf of lead author Gerald Andriole, MD, of Washington University, who was not able to attend the session.

Investigators measured levels of PCA3 and serum PSA in 1,308 men receiving dutasteride and 1,554 men receiving placebo-a subset of the study's participants. At 2 years, the median PCA3 score in the dutasteride group was 16.2, whereas it was 17.2 in the placebo group. At 4 years, the median PCA3 score was 18.8 in the dutasteride group and 18.1 in the placebo group. The differences were not statistically significant.

'Significant' difference in PSA levels

That's in contrast to median serum PSA levels, which at 2 years were only a median of 2.2 ng/mL for the men taking dutasteride compared with 5.4 ng/mL in the placebo group, a significant difference. At 4 years, the difference was also significantly different, with the median serum PSA at 2.0 ng/mL in the dutasteride group versus 5.9 ng/mL in the placebo group.

At the PCA3 cutoff of 35, the sensitivity and specificity of the cutoff for predicting biopsy outcome were 41% and 81%, respectively, at 2 years in the dutasteride group, and 55% and 79%, respectively in the placebo group. At 4 years, sensitivity and specificity of the cutoff for predicting biopsy outcome were 35% and 75%, respectively for the dutasteride group and 35% and 78%, respectively for the placebo group.

The study was limited by not having baseline PCA3 determinations in the men.

"This is really a population model looking at the control and the active treatment arms of the REDUCE trial," said Dr. Strope.

"We don't know on the individual patient level what the change would be," he added.

Dr. Andriole and study co-authors disclosed financial and/or other relationships with GlaxoSmithKline and Gen-Probe, Inc., both of which provided funding for the study.