PCA3 Beats PSA in Predicting Prostate Biopsy Outcomes
SAN FRANCISCO—The prostate cancer gene 3 (PCA3) molecular urine test is more accurate than the PSA test in predicting outcomes of repeat biopsies, new findings confirm.
PCA3 correlated with biopsy Gleason score, providing additional evidence that PCA3 might be useful for identifying more aggressive prostate cancer, researchers reported here today at the Genitourinary Cancers Symposium.
Jack Groskopf, PhD, Director of Research and Development, Cancer Diagnostics, Gen-Probe,, Inc., San Diego, and colleagues studied men in the placebo arm of the REDUCE (Reduction by Dutasteride of Prostate Cancer Events) trial, a four-year study examining whether dutasteride reduces the risk of prostate cancer.
All subjects in the trial had negative biopsy results at baseline and a serum PSA level of 2.5-10 ng/mL. Ten-core biopsies were obtained after two and four years. The researchers determined PCA3 scores on 1,140 urine specimens from men scheduled for biopsies at two and four years.
A total of 1,072 (94%) specimens had enough RNA for PCA3 analysis. Of these, 18% were biopsy positive for prostate cancer. As PCA3 scores increased, so did the likelihood of positive biopsy results, said Leonard S. Marks, MD, Professor of Urology at the David Geffen School of Medicine at the University of California-Los Angeles, who presented study findings. Prostate cancer was detected in 6% of men with a PCA3 score below 5 and in 57% of men with a score above 100.
In addition, PCA3 measurements at year 2 of the study significantly predicted year 4 biopsy outcomes, and serum PSA and free PSA did not, Dr. Marks told attendees. A PCA3 threshold of 35—which he said offers the best combination of sensitivity and specificity—had a sensitivity and specificity of 36.4% and 79.1%, respectively.
PCA3 scores were significantly higher for men with a Gleason score of 7 or higher compared with lower scores. The median PCA3 score was 49.5 for patients with a Gleason score of 7 or above compared with 31.8 among those with a Gleason score below 7.