New blood test appears more accurate and promising for reducing unnecessary prostate biopsies
A presentation of a preliminary study at last year’s American Urological Association (AUA) annual meeting, confirmed the findings of that study at the 2018 AUA meeting held in San Francisco. The findings showed that the IsoPSA test, an investigational blood assay predicting a man’s risk of high-grade prostate cancer, is more accurate than the standard prostate specific antigen (PSA) test. This news is from a prospective validation study showing that it has the potential to reduce the number of unnecessary prostate biopsies substantially.
Last year the study looking at the IsoPSA test found that it detected prostate cancer more precisely than current tests in two crucial measures – distinguishing cancer from benign conditions, and identifying patients with high-risk disease. Now that the study has been validated, the use of IsoPSA may reduce the need for biopsy, and may lower the likelihood of overdetection and overtreatment of nonlethal prostate cancer.
The validation study from the Cleveland Clinic’s Glickman Urological and Kidney Institute, included 271 patients. Each patient had blood drawn for the IsoPSA analysis within 30 days of a prostate biopsy. Discovered was the IsoPSA had a 94% sensitivity for detecting high-grade (Gleason score of 7 or higher) cancer and a 93% negative predictive value for high-grade cancer. A low IsoPSA number means about a 93% chance a man doesn’t have high-grade prostate cancer. From these results, it showed 47% of prostate biopsies could have been avoided if using an IsoPSA test.
Men included in the validation study had also underwent magnetic resonance imaging (MRI)-guided prostate biopsy – which has been shown to improve detection of high-grade prostate cancer – in addition to the IsoPSA test. When both MRI and IsoPSA together were used, they accurately predicted the presence of high-grade cancer about 86% of the time which is better than the standard PSA test and free PSA.
The IsoPSA test is based on the fact that proteins produced by cancer cells have different 3D structures (isoforms) than the same proteins produced by normal cells. IsoPSA measures all of the different molecular isoforms in serum PSA, and it doesn’t matter which isoforms are present.
By using the IsoPSA test over the standard PSA test, this can be a good way to reduce the use of MRI scans which can miss about 20% of high-grade cancers. If a man has a negative IsoPSA test result, then this would mean with 93% accuracy that high-grade cancer is not present and therefore he would most likely not need an MRI scan.
Another advantage of the IsoPSA test is that any hospital lab can use it for fast results. Currently available tests require that blood specimens be sent to a central lab which can take several days for the results to be faxed or emailed to a doctor’s office. The IsoPSA test is a simple blood draw and the results can be sent directly to an electronic medical record system inbox. Generally, most electronic medical record systems have a feature in which the doctor can directly message a patient to explain the results of a test and to outline the plan of treatment.