Novel assay may help identify prostate Bx candidates
Test could reduce unnecessary biopsies by 47%, interim study data indicate
A simple blood test that measures PSA structure rather than concentration may be more accurate than PSA in identifying men who need a prostate biopsy, according to the results of a study presented at the Genitourinary Cancers Symposium in Orlando, FL.
IsoPSA is a novel structure-based protein assay that uses water as an experimental probe for changes in PSA structure. The assay produces a single quantitative parameter, K, describing the overall composition of the complex PSA isoforms, using step partitioning of proteins into two aqueous phases. The ratio of the overall complex PSA concentrations in the two phases differentiates between patients with high-grade disease and those with benign or low-grade disease.
Interim data from the study testing the use of IsoPSA were presented by Eric A. Klein, MD, chairman of Glickman Urological and Kidney Institute at Cleveland Clinic.
According to Dr. Klein, it is important to distinguish low-grade disease from high-grade disease because patients with low-grade cancers are generally not treated immediately and are instead placed on an active surveillance protocol. In contrast, high-grade cancers are usually treated since they have the potential to metastasize and be lethal.
In the past, PSA levels have been used to determine whether a prostate biopsy is needed. However, according to Dr. Klein, PSA is prostate specific but not prostate cancer specific, so its use can be confusing.
“Most men with an ‘elevated PSA’ actually have benign prostatic hyperplasia and not prostate cancer, such that many men are biopsied unnecessarily. Our data suggests that IsoPSA more accurately identifies those men who actually have cancer so that only those with a high suspicion of cancer will be biopsied,” Dr. Klein told Urology Times.
For the study, the authors obtained 217 plasma samples from patients previously selected for prostate biopsy. Patients had blood PSA between 2.0 ng/mL and 44.0 ng/mL. IsoPSA was evaluated within 90 days of collection against 12-core biopsy results classified as Gleason of 7 or greater (n=72) or other (either benign or Gleason=6; n=145). The prevalence of high-grade disease was 33%.