Percent free prostate-specific antigen (PSA) is an accurate predictor of prostate cancer risk in men with serum PSA 2.5 ng/mL and lower

BACKGROUND. Up to 17% of men with a prostate-specific antigen (PSA) level below the accepted prostate biopsy cutoff of 2.5 ng/mL may have prostate cancer. Because identification of these patients represents a difficult task, we assessed the ability of percent free PSA to discriminate between benign and malignant prostate biopsy outcomes in men with PSA ≤2.5 ng/mL. METHODS. Between 1999 and 2006, 543 men with a PSA ≤2.5 ng/mL were referred for initial prostate biopsy. Age, total PSA, percent free PSA, and digital rectal examination findings represented predictors of prostate cancer at biopsy in logistic regression models. The area under the receiver operating characteristics curve (AUC) quantified the discriminative ability of the predictors. The pathological characteristics of the detected cancers were assessed in individuals treated with radical prostatectomy. RESULTS. Of all, 23% had prostate cancer on biopsy, 16.5% of patients treated with radical prostatectomy had pT3 stage, and 35.6% had a pathological Gleason score of 3 + 4 or higher. The most accurate predictor of prostate cancer on biopsy was percent free PSA (0.68) versus age (0.50), total PSA (0.57), or rectal examination findings (0.58). Of patients with percent free PSA below 14%, 59% had prostate cancer. In multivariate models, percent free PSA (P