The role of urine prostate cancer antigen 3 mRNA levels in the diagnosis of prostate cancer among Hong Kong Chinese patients.

OBJECTIVE To establish and verify the utility of measuring urine prostate cancer antigen 3 (PCA3) mRNA levels in the diagnosis of prostate cancer among Hong Kong Chinese patients. DESIGN Cross-sectional study. SETTING Urology Unit of a regional hospital in Hong Kong. PATIENTS This study was carried out in two parts. In the first part, 102 post-prostatic massage urine samples were collected from patients with known prostate cancer (38 patients) and controls (64 patients, with normal digital rectal examination and serum prostate-specific antigen <4 ng/mL). The urine levels of PCA3 and prostate-specific antigen mRNA were measured and the best cut-off point for differentiating cancer was determined. In the second part of the study, post-prostatic massage urine samples from 47 patients with clinically suspected prostate cancer were collected prior to prostate biopsy. The performance of PCA3 as a diagnostic aid for cancer was then assessed using the aforementioned cut-off value. RESULTS In the first part of the study, the best cut-off for the PCA3 ratio (defined as the ratio of the Ct value of PCA3/PSA mRNA) was 1.127. Applying this cut-off to the 47 patients with clinically suspected prostate cancer and no history of previous prostate biopsy, the sensitivity and specificity of PCA3 for diagnosing prostate cancer were 71% and 92%, respectively. CONCLUSION The post-prostatic massage urine PCA3 level shows utility for diagnosing prostate cancer in patients with elevated prostate-specific antigen levels that could facilitate decisions to undertake prostate biopsy and avoid unnecessary biopsies.