Video
Clinical Validity and Utility of an Exosome-Based Urine Biomarker Test
Author(s):
An overview of the clinical validity and utility of a urine-based, exosomal molecular test for prostate cancer screening and risk assessment.
Patient Case: A 64-Year-Old Man with Elevated PSA Levels
- A 64-year-old-man underwent PSA testing during his annual physical with his primary care physician; PSA was 5.6 ng/mL and PSA density was 0.16.
- He then saw a urologist, who ordered a multiparametric MRI; result was PI-RADS 4.
- The patient was reluctant to undergo a prostate fusion biopsy, therefore the patient’s urologist recommended that he undergo exosome-based molecular testing to help determine risk of prostate cancer; his test score was 16.3.
- The patient and urologist remained concerned about his PI-RADS 4 MRI score. The urologist also noted that the PSA density of 0.16 was slightly above the threshold of 0.1.
- The patient elected to undergo TRUS-guided biopsy, which was negative for prostate cancer.
Judd W. Moul, MD, FACS: The ExoDx test has had a lot of validation and a lot of research done. It was validated in a large study that was published in JAMA Oncology, and then a number of subsequent validations including a large European study. When the company took those data to the FDA, the test was cleared and is commercially used for patients who have a total PSA [prostate-specific antigen] between 2 and 10 [ng/mL] in men who are 50 years of age or older. That is the labeled indication for the exosome test, men who have a total PSA between 2 and 10 [ng/mL] who are being screened for prostate cancer and are 50 years of age or older.
When we are talking about sensitivity and specificity, and negative predictive value and positive predictive value, it really becomes confusing, not only for us as clinicians, but for our patients and even for experienced clinicians and researchers.
In a general population in which you are using the exosome urine test, we expect about 20% to 25% of the patients to have a normal value, meaning they would have the exosome urine test come back less than 15.6, which is the upper limit of normal. Those men have a very low likelihood of having clinically important Gleason 7 [score] or higher prostate cancer. In fact, the negative predictive value was 92%, indicating that if you avoid a prostate biopsy in all those men who have a normal exosome test, you would only miss 8% who could have Gleason 7 or higher. Again, a 92% negative predictive value equates to an 8% risk of Gleason 7. That’s at least 20%, or pretty much of 1 out of 5 patients in your practice who would be referred to you with an elevated PSA where you could potentially avoid a biopsy. Or if you are not always using MRI, you could potentially avoid the MRI in those patients as well and reassure them, and perhaps see them back for a repeat test in 6 to 12 months as opposed to an immediate biopsy or immediate MRI.
Transcript edited for clarity.
