REPEAT ULTRASOUND-GUIDED PROSTATE NEEDLE-BIOPSY - USE OF FREE-TO-TOTAL PROSTATE-SPECIFIC ANTIGEN RATIO IN PREDICTING PROSTATIC-CARCINOMA

Purpose: Despite being the most useful tumor marker for the diagnosis of patients with prostate cancer, serum prostate specific antigen (PSA ) is still hampered by lack of specificity. A negative prostate biopsy is associated with a 20 to 40% incidence of positive repeat biopsy in men with persistently elevated serum PSA levels. We determine whether the free-to-total PSA ratio could be predictive of prostate cancer in men undergoing repeat biopsy. Materials and Methods: Archival sera, d rawn before the first biopsy, were gathered from 51 men with a total s erum PSA of 2 to 15 ng./ml. who underwent repeat prostate needle biops y for various indications. The percent free PSA was calculated using t he Hybritech Tandem-R dagger free and total PSA as well as Dianon Syst ems free double dagger and Hybritech total PSA assays. The free-to-tot al PSA ratio results between the cancer and noncancer groups were comp ared using Student's t test. Results: The median Hybritech free-to-tot al PSA ratio was significantly lower in patients with positive repeat prostate needle biopsy compared to those with negative biopsy (14.9 ve rsus 19.4%, p = 0.05). Total PSA as well as the percent Dianon free-to -Hybritech total PSA ratio were not significantly different between th e 2 groups of men. Conclusions: For total PSA in the range of 2 to 15 ng./ml. Hybritech free-to-total PSA ratio appeared to aid in the predi ction of cancer on repeat biopsy.