Received on November 8, 2005
Accepted on March 28, 2006

Cancer Diagnostics

Aptima PCA3 Molecular Urine Test: Development of a Method to Aid in the Diagnosis of Prostate Cancer

¹ Gen-Probe Incorporated, San Diego, CA
² Urological Sciences Research Foundation, Culver City, CA

^* To whom correspondence should be addressed. E-mail: jackg{at}gen-probe.com.

Background: Prostate cancer antigen 3 (PCA3) is a noncoding prostate-specific mRNA that has shown promise as a prostate cancer diagnostic tool. This report describes the characterization of a prototype quantitative PCA3-based test for whole urine.

Methods: Whole-urine specimens were collected after digital rectal examination from 3 groups: men scheduled for prostate biopsy (n = 70), healthy men (<45 years of age with no known prostate cancer risk factors; n = 52), and men who had undergone radical prostatectomy (n = 21). PCA3 and prostate-specific antigen (PSA) mRNAs were isolated, amplified, and quantified by use of Gen-Probe DTS400^® Systems. Prostate biopsy results were correlated with the PCA3/PSA mRNA ratio, and PSA mRNA concentrations were used to normalize PCA3 signals and confirm the yield of prostate-specific RNA. Assay precision, specimen stability, and mRNA yield were also evaluated.

Results: The specimen informative rate (fraction of specimens yielding sufficient RNA for analysis) was 98.2%. In this clinical research study, ROC curve analysis of prebiopsy specimens yielded an area under the curve of 0.746; sensitivity was 69% and specificity 79%. Serum PSA assay specificity was 28% for this same group. PCA3 and PSA mRNA were undetectable in postprostatectomy specimens except for one man with recurrent prostate cancer. Assay interrun CVs were 12%. Both mRNAs were stable in processed urine up to 5 days at 4 °C and after 5 freeze-thaw cycles.

Conclusion: The Aptima^® PCA3 assay combines simple specimen processing with precise assays and existing instruments and could add specificity to the current algorithm for prostate cancer diagnosis.