additional story 3/7PCA3 Urine Test Predicts Prostate Cancer Biopsy Results: Presented at ASCO-GU
By Fred Gebhart
SAN FRANCISCO -- March 7, 2010 -- A prospective analysis of more than 1,000 patients found that a urine-based test for prostate cancer gene 3 (PCA3) could accurately predict the results of a prostate biopsy.
Results confirm earlier small trials suggesting that PCA3 is more predictive of prostate biopsy results than standard prostate-specific antigen (PSA) testing, researchers said here at the 2010 Genitourinary Cancers Symposium (ASCO-GU).
"PCA3 is over expressed in 95% of all prostate cancers by 60- to 100-fold compared with normal tissue," said Leonard Marks, MD, University of California Los Angeles Geffen School of Medicine, Los Angeles, California, on March 5. "These results confirm that PCA3 is more closely associated with prostate cancer than is PSA."
Researchers evaluated PCA3 among 1,140 men in the placebo arm of the 4-year Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial to test the use of dutasteride to reduce risk for prostate cancer. The placebo arm was used because the men entered the trial with negative prostate biopsies and were already scheduled for repeat 10-core biopsies at year 2 and 4.
During the trial, urine specimens were collected immediately following digital rectal exam, frozen, and analysed at a central lab. The resulting PCA3 score was significantly correlated with a positive prostate biopsy result. Among men with a PCA3 score <5, only 6% had a positive prostate cancer diagnosis; among men with a PCA3 score >100, 57% were diagnosed with cancer (P < .0001).
Higher PCA3 scores also correlated with more aggressive cancers as determined by Gleason scores <7 or >=7 (P = .0017). In addition, PCA3 at year 2 was correlated with positive biopsy results at year 4 (P = .0002), while neither serum PSA nor free PSA were predictive of biopsy outcome (P = .328 and P = .678, respectively). Dr. Marks said the REDUCE results are similar to the results of earlier and smaller trials.
"A very low score gave a very low risk for prostate cancer and a high score was very indicative of cancer," he said. "In practical terms, this tells us that even if a biopsy is negative, a high score means that there is probably a tumour that we missed."
The appropriate cutoff for concern appears to be 35, he added. That level provides a useful combination of 58% sensitivity and 72% specificity. PCA3 levels are not affected by benign prostatic hyperplasia or by prostatitis, both of which can elevate PSA levels.
The conference is sponsored by the American Society of Clinical Oncology (ASCO), the American Society for Therapeutic Radiation Oncology (ASTRO), and the Society of Urologic Oncology (SUO).
[Presentation title: Validation of the PCA3 Molecular Urine Test for Predicting Repeat Prostate Biopsy Outcome in the Placebo Arm of the Dutasteride REDUCE Trial. Abstract 5]
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