UroToday - In Urologia Internationalis, a group headed by Dr. Arnulf Stenzl report on the use of the prostate cancer gene 3 (PCA3) test in their clinical practice in Tübingen, Germany. PCA3 detects the untranscribed mRNA of the gene, which does not encode for a protein. PCA3 is expressed almost exclusively in prostate tissue. Compared with benign prostate tissue, prostate cancer (CaP) demonstrates overexpression in 95% of cases.

Between 2006 and 2008, the PCA3 test was performed on 104 consecutive patients in the authors' urology clinic. Their indications for the PCA3 test were a previous negative prostate biopsy but persistently elevated PSA, increasing PSA below 4ng/ml, elevated PSA and underlying prostatic condition such as LUTS or patient request for the test. An abnormal DRE or PSA >4ng/ml at initial presentation were indication for prostate biopsy without the PCA3 test. A PCA3 score >35 were discussed with the patient as the indication for prostate biopsy. The PCA3 urine sample was collected following the manufacturer's recommended protocol for the prostate exam.

A total of 32 patients underwent 10-core prostate biopsy, and two had an MRI guided biopsy. In patients undergoing repeat prostate biopsy, the sampling pattern included two transition zone samples. Among the PCA3 samples, one had no detectable PSA mRNA. This left 103 evaluable tests, and the cost per test was 180 Euros. The median PCA3 score was 32 and no statistically significant correlation between PCA3 score, PSA value, and volume of the prostate was found. Using a positive cutoff of 35, 56 patients had a negative test and 47 had a positive test.

Among the 32 patients having a biopsy based upon the PCA3 test result, 14 had 1 or more previously negative prostate biopsies. Prostate cancer was detected in 18/32 patients (56%). Both patients having MRI guided biopsies were found to have CaP. Among the 14 patients with previous negative biopsies, 8 were found to have CaP (57%).

In patients with a negative biopsy, the median PCA3 score was 26 and in men with a positive biopsy it was 80.5. Sensitivity for CaP detection for patients with a PCA3 score >35 was 94% and specificity was 36%. The negative and positive predictive values were 83% and 65%, respectively. Using a PSA cutoff of 2.5ng/ml, the negative predictive value was 50% and the positive predictive value was 57%. Four of 14 men with a negative biopsy had a negative PCA3 score but increased PSA level and 1 man had a positive PCA3 score but a negative PSA value. Eight of the 14 negative biopsy patients had false-positive values for both the PCA3 and PSA tests. The AUC for the ROC curve was .81 for PCA3 and .061 for PSA.

Schilling D, Hennenlotter J, Munz M, Bökeler U, Sievert KD, Stenzl A
Urol Int. 2010 Apr 27. Epub ahead of print.
doi: 10.1159/000314078

UroToday Contributing Editor Christopher P. Evans, MD, FACS

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