Is PCA3 any more useful than a PSA test in the “real world”?

At major academic medical centers and in at least one large clinical trial, the prostate cancer gene 3 or PCA3 test has appeared to work better than the total serum PSA test as a means to  predict the presence of prostate cancer on biopsy.

There are now data from a small Swedish community-based study that sought to validate the diagnostic precision of the commercially available Progensa™ PCA3 test compared to the serum PSA test in a series of mixed patients who had no prior history of prostate cancer. This patient cohort included patients with previous negative biopsies.

The study included 62 men scheduled for prostate biopsy. Urine samples were obtained from a series of 62 men, all scheduled for a prostate biopsy at Skåne University Hospital in Malmö, Sweden, according to recommended protocol. Data from the urine samples were compared to PSA data and the results of the biopsies for all 62 patients.

The results of this analysis were as follows:

  • Prostate cancer was found in 18/62 patients (29 percent).
  • A one-step increase in PCA3 was linked to a small but signficant increase in the odds of cancer diagnosis (odds ratio [OR] = 1.026).
  • Differences in the odds ratio between PCA3 and total serum PSA were not statistically significant.
  • A model using both PCA3 and total serum PSA did not increase the likelihood of accurate predication of prostate cancer.
  • There was no significant correlation between PCA3 levels, total serum PSA levels, and/or prostate volume.

Now this is a small study and it was based on a mixed set of patients, but the authors conclude that, “This study does not support a role for the [PCA3] test to replace or be added to [total serum] PSA” in assessing risk for prostate cancer detection on biopsy.

The “New” Prostate Cancer InfoLink does not think this is by any means the end of this discussion. We have commented on this paper primarily to point out that what can be shown in large, academic clinical trials does not always and easily “translate” into practical value day to day in the real world. It may be a while before we truly understand how best to take advantage of data from PCA3 testing in patients at risk for prostate cancer in the community setting.

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