FREE AND COMPLEXED PROSTATE-SPECIFIC ANTIGEN SERUM RATIOS TO PREDICT PROBABILITY OF PRIMARY PROSTATE-CANCER AND BENIGN PROSTATIC HYPERPLASIA

Objectives. Ratios of free to total prostate-specific antigen (f/t PSA ratio) improved differentiation of benign prostatic hyperplasia (BPH) from prostate cancer (CaP). Using sera obtained at least 1 month prio r to biopsy-confirmed diagnosis and logistic regression adjusted for d isease prevalence, probability curves are constructed to predict the p resence of CaP. Methods. The patient population included 122 (44%) BPH sera and 155 (56%) prostate carcinoma sera collected prior to any the rapy. The total PSA range = 2.0-20.0 ng/mL; median age = 69 years, Ext ernal reference standards for both free and total PSA assays were used to standardize the assays and correct the ratio. Probability curves a nd tables for cancer incidence were formulated for a subset of the tot al test population (total PSA range = 2.0-10.0 ng/mL; 98 BPH, 118 CaP patients) by using logistic regression and prior cancer prevalence sta tistics derived from it published patient screening study. Results. Me dian f/t PSA ratios were 0.18 and 0.12 in the overall sample and 0.19 and 0.12 in the subset for BPH and CaP, respectively (P = 0.0001). The median total PSA concentrations for BPH and CaP were 5.8 and 6.7 ng/m L when total PSA range = 2.0-20.0 ng/mL and were 4.9 and 5.9 ng/mL whe n total PSA range = 2.0-10.0, respectively. Conclusions. Cancer probab ility curves were constructed to help guide decisions concerning biops y and other aspects of prostate cancer disease management. Further val idation of this approach in another series of patients is necessary an d is planned. Copyright 1996 by Elsevier Science Inc.