The studies were presented at the American Society of Clinical Oncology’s (ASCO) Genitourinary (GU) Cancers Symposium in San Francisco.

In the two studies, PCA3 was used to test urine samples from men enrolled in the Reduce trial of GlaxoSmithKline’s drug dutasteride. PCA3 testing was done on urine samples from 1,140 men in the placebo arm of the Reduce trial, and from 1,308 men in the dutasteride arm. All men underwent prostate biopsies two and four years after enrollment.

The first PCA3 study presented was originated from the placebo arm of the Reduce trial. The study showed that PCA3 scores were correlated with a positive prostate biopsy result (P<0.0001), and that men who had higher PCA3 scores were more likely to have prostate cancer. Specifically, cancer was diagnosed in only 6% of men with low PCA3 scores, but in 57% of men with high PCA3 scores.

The second PCA3 study presented was originated from the dutasteride arm of the Reduce trial. This study showed that PCA3 also can be used to predict prostate biopsy outcomes in men taking dutasteride. In contrast to serum PSA testing, median PCA3 scores were equivalent in the placebo and dutasteride groups, and PCA3 sensitivity and specificity were also similar between the two groups.

The second study also confirmed earlier research that showed PCA3 outperforms serum PSA testing for prostate cancer detection, and improves diagnostic accuracy when combined with serum PSA testing and other clinical information. Studies have shown that as PCA3 is highly specific for prostate cancer, it predicts the results of repeat biopsies more accurately than traditional prostate-specific antigen (PSA) testing.

Gen-Probe’s Progensa PCA3 assay, which has been CE-marked for sale in the European Union, is the first urine-based molecular diagnostic assay for prostate cancer. In August of 2009, Gen-Probe initiated a clinical trial intended to secure US regulatory approval of the assay for use on its semi-automated instrument system. The company remains on track to file a Premarket Approval Application later this year.

Data from approximately 30 peer-reviewed publications suggest that the Progensa PCA3 assay, when used with other patient information, may help address some of the well-known challenges urologists face when identifying prostate cancer, such as minimizing unnecessary biopsies.

Eric Lai, senior vice president of research and development of Gen-Probe, said: “These two studies, which involved more than 2,400 men, are the significant studies conducted as far of our Progensa PCA3 molecular urine test, and confirm the assay’s ability to predict the outcome of a repeat prostate biopsy, thereby helping physicians provide more appropriate, personalized patient care.”