The influence of prostate volume on the prostate-specific antigen (PSA) level adjusted for the transition zone volume and free-to-total PSA ratio: a prospective study

Objectives To evaluate the influence of prostate volume on the prostate-spe cific antigen (PSA) level adjusted for the transition zone volume (PSAT) an d free-to-total PSA ratio (f/tPSA) in detecting prostate cancer in men with intermediate PSA levels of 4.1-10.0 ng/mL. Patients and methods From March 1997 to June 1999, the f/tPSA and PSAT were measured in 105 patients who underwent ultrasound-guided systemic biopsies and had a PSA level of 4.1-10.0 ng/mL, with an apparently normal prostate on a digital rectal examination. The PSAT and f/tPSA were evaluated in all patients and in subgroups of patients with small (< 40 mL) or large (greate r than or equal to 40 mL) prostates, using receiver operating characteristi c (ROC) curves. Results Total prostate volume was highly correlated with transition zone vo lume in all patients and in both subgroups (P < 0.001). In all 105 patients , PSAT had a sensitivity of 82% and its use would have avoided the largest number of unnecessary biopsies (87% specificity) at a threshold value of 0. 35 ng. In men with small prostates f/tPSA and PSAT had a high sensitivity a nd specificity, at threshold values of 0.12 and 0.35 ng, respectively. In l arge prostates the PSAT was superior to f/tPSA in detecting prostate cancer . Conclusions These results suggest that both f/tPSA and PSAT are useful in d etecting prostate cancer in men with small prostates, while PSAT is superio r to f/tPSA in detecting prostate cancer in men with large prostates.