A new, urine-based screening test known as the PSA/SIA assay may be more sensitive than traditional methods in detecting prostate cancer.
Developed by the Cleveland, Ohio-based biotechnology company AnalizaDx, Inc., and studied by researchers at the Seidman Cancer Center at University Hospitals (UH) Case Medical Center and the Cleveland Clinic (both also in Cleveland), the prostate-specific antigen/solvent interaction analysis (PSA/SIA) test is described as a novel prostate cancer assay that focuses on changes to the structure of PSA.
“This test provides a new way to look at prostate cancer diagnosis utilizing a novel biological assay which differentiates PSA molecular structures arising from cancer versus noncancerous glands,” affirmed Mark Stovsky, MD, principal investigator and lead author of the study, in a statement describing the findings, which will appear in the September 2011 issue of Urology.
Stovsky—a urologist at UH Case Medical Center and associate professor of urology at Case Western Reserve University School of Medicine—led a study of 222 men undergoing prostate biopsy. The 100 malignant biopsies were classified as case; the 122 benign were the controls. At a cutoff value of k =1.73 (with k being a structural index whose numerical value is defined as the ratio of the concentration of all PSA isoforms), PSA/SIA displayed 100% sensitivity (no false-negative results) and 80.3% specificity (low false-positive results).
As noted in the statement issued by UH Case Medical Center, the accuracy of traditional PSA testing is limited by both relatively high false-positive rates of approximately 55% to 75% and false-negative rates of up to 15%. False positives lead to unnecessary biopsies and worry on the part of patients, whereas false negatives cause clinicians to miss cancer in men with “normal” PSA values.
Rather than attempting to find a single genetic biomarker (PSA) that predicts the presence of prostate cancer, the PSA/SIA assay works by separating PSA protein structures on the basis of being linked to either a “cancer” or a “noncancer” pathologic diagnosis based on ultrasound-guided biopsy.
“In this preliminary study, analysis of the overall structurally heterogenous PSA isoform population using the SIA assay showed promising results to be further evaluated in future studies,” concluded the investigators.