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

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Abstract
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, drawn before the first biopsy, were gathered from 51 men with a total serum PSA of 2 to 15 ng./ml. who underwent repeat prostate needle biopsy for various indications. The percent free PSA was calculated using the Hybritech Tandem-R [dagger] free and total PSA as well as Dianon Systems free [double dagger] and Hybritech total PSA assays. The free-to-total PSA ratio results between the cancer and noncancer groups were compared using Student's t test. Results: The median Hybritech free-to-total PSA ratio was significantly lower in patients with positive repeat prostate needle biopsy compared to those with negative biopsy (14.9 versus 19.4%, p = 0.05). Total PSA as well as the percent Dianon free-to-Hybritech total PSA ratio were not significantly different between the 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 prediction of cancer on repeat biopsy.