The Role of Liquid Biomarker for Early Detection of Prostate Cancer - Episode 2
Experts urologists, David Albala, MD and Judd W. Moul, MD, compare the utility of a variety of blood and urine tests for screening and diagnosing prostate cancer.
David Albala, MD: A variety of other tests have been commercially available; for example, the Prostate Health Index and the 4Kscore. These are blood tests. And we’ve seen an explosion in the last couple of years with urine-based tests, like SelectMDx, the PCA3 [prostate cancer antigen 3] test—which has been around for quite some time—and now exosome ExoDx is the new kid on the block. Let’s say I’m a urologist just starting my career. I have a variety of choices. How do you try to pick 1 test vs another, and how do you use those in combination with the PSA [prostate-specific antigen] test and the rectal exam that we’ve traditionally been taught to do?
Judd W. Moul, MD: That’s a great question. That’s a lot of information to cover. Let me back up and say that if I’m a urologist starting in practice, 1 thing that we’ve seen—or that I’ve seen in my 30 years doing this—is that many patients are more sophisticated. When they’re presented with an elevated PSA, especially a borderline PSA or a gray zone PSA, many patients want more data before they’re willing to undergo an invasive biopsy. So if I’m starting in practice, I’d want to be comfortable with some of the secondary tests that could be done between an elevated PSA and a biopsy.
We employ a number of these secondary tests. Our go-to first-line secondary test is Prostate Health Index blood test. Part of that is because that’s done in-house at our institution, so from a practical standpoint, we’re able to get that right away, and we’ve even started to deploy that and train primary care physicians—in some cases, the ones who are comfortable with it—to do that test. We’ve also been through and had a lot of experience with the urine tests. When I first came to Duke Cancer Center, and even before Duke at Walter Reed Army Medical Center, we were using the PCA3 urine test. That was the first urine test that we all had as a secondary to PSA. I’m sure you and I both met with Dave Bostwick and Bostwick Laboratories. He did great work with promoting that test. Unfortunately that was a first-generation urine test, and did not stand the test of time. The data were not bad, but it wasn’t as robust, so that fell by the wayside.
You mentioned some of the secondary urine tests , including the exosome ExoDx diagnostics test and the SelectMDx test. We use the exosome test at Duke as our secondary urine test. That was the test that replaced PCA3, and we’ve been pretty happy with it. The bottom-line message is that if I’m a new urologist, or a urologist who does a lot of PSA work, in my opinion you need to get comfortable with at least 1 secondary blood test and 1 secondary urine test to do the best job with your patients.
David Albala, MD: That’s what we’ve done. We’ve embraced the 4Kscore test, for example, which looks at 4 types of isoenzymes: total PSA, free PSA, intact PSA, and HK2. If patients have a cutoff of 7.5% or higher, then those patients would be considered much higher risk or have a higher likelihood of prostate cancer. Like you, we’ve done the urine tests as well, and the beauty of the urine tests is that the accuracy is quite good. They stand the test of time. The SelectMDx test is a little different because you have to do a rectal examination in those patients before you collect the urine; the exosome ExoDx test is a little nicer because you don’t have to do a rectal exam. Your advice is great: Be familiar with these tests and have an understanding, because patients don’t want to get biopsies. There are risks associated with biopsies. So consider tests before subjecting those patients to the risk of either an infection or bleeding. Honestly, I’ve never had a prostate biopsy myself, but I’ve done enough to understand that they’re uncomfortable. Even in the best of hands, with a good block, there’s still some discomfort.
Transcript edited for clarity.