PCA3: a new tool to diagnose prostate cancer (PCa) and a guidance in biopsy decisions. Preliminary report of the UrOP study.

OBJECTIVES: PCA3 is a prostate specific non-coding mRNA that is significantly overexpressed in prostate cancer tissue. Urinary PCA3 levels have been associated with prostate cancer grade suggesting a significant role in the diagnosis of prostate cancer. We measured urinary PCA3 score in 925 subjects from several areas of Italy assessing in 114 the association of urinary PCA3 score with the results of prostate biopsy.

MATERIAL AND METHODS: First-catch urine samples were collected after digital rectal examination (DRE). PCA3 and PSA mRNA levels were measured using Trascription-mediated PCR amplification. The PCA3 score was calculated as the ratio of PCA3 and PSA mRNA (PCA3 mRNA/PSA mRNA x 1000) and the cut off was set at 35.

RESULTS: A total of 925 PCA3 tests were performed from December 2008 to January 2010. The rate of informative PCA3 test was 99%, with 915 subjects showing a valid PCA3 score value: 443 patients (48.42%) presented a PCA3 score >/= 35 (cut-off) whereas the remaining 472 patients (51.58%) presented a PCA3 score lower the cut-off limit (< 35). Of the 443 patients with PCA3 score >/= 35, 105 (23.70%) underwent biopsy or rebiopsy. We found that 27 patients (25.71%) had no tumour at biopsy, 37 (35.24%) had HGPIN or ASAP and 41 (39.05%) had a cancer. Moreover, including the additonal 9 patients with PCA3 < 35, who underwent biopsy post PCA3 results, our data indicate that patients with negative biopsy (n = 31) show lower PCA3 score (mean = 54.9) compared with patients with positive biopsy (n = 45) (mean = 141.6) (p = 0.000183; two-tailed t-student test). The mean PCA3 score (79.6)for the patients diagnosed with HGPIN/ASAP at biopsy (n = 38) was intermediate between patients with negative and positive biopsy.

CONCLUSIONS: Our results indicate that the PCA3 score is a valid tool for prostate cancer detection and its role in making better biopsy decisions. This marker consents to discriminate patients who have to undergo biopsy from patients who only need be actively surveilled: Quantitative PCA3 score is correlated with the probability of a positive result at biopsy.