SEATTLE--A study of 1,695 cancer-free men found that PSA density provides a far more accurate screening assay for detection of prostate cancer than PSA serum concentration, Robert Kane, MD, of Harvard Medical School, said at the Pacific Northwest Cancer Foundation Meeting on Transperineal Brachytherapy for Early Stage Prostate Cancer.
PSA density is calculated by relating the serum PSA concentration (ng/mL) to the volume of the prostate gland in a particular patient.
Serum PSA testing is very useful for following patients with known prostate cancer, to assess the effectiveness of therapy and the progression of the cancer, Dr. Kane said. But for prostate cancer surveillance, the considerable number of false-positives in men who simply have enlarged glands results in emotional cost to the patient and substantial economic cost to the health-care system.
Lacks Specificity in Both Directions
The serum PSA test also lacks specificity in the other direction. Dr. Kane reported that in several studies, 23% to 43% of patients with organ-confined prostate cancer had normal PSA values.
The multicenter study, conducted by Dr. Kane and other investigators as part of the American Cancer Society National Prostate Cancer Detection project (Cancer, March 1, 1992), analyzed the distributions of PSA concentrations in cancer-free men overall and also according to differing prostate gland volumes, patient age, and the presence or absence of symptoms of benign prostatic hypertrophy (BPH).
They found that neither age nor symptoms of BPH appeared to have any effect on PSA levels when adjusted for gland volume. They concluded that estimating PSA density (based on ng/mL/cc gland volume) rather than relying on absolute serum levels may make it possible to reduce the number of false-positive PSA results in the general population.