Comparison of percent free PSA, PSA density, and age-specific PSA cutoffs for prostate cancer detection and staging

Abstract

Objectives: Various methods have been proposed to increase the specificity of prostate-specific antigen (PSA), including age-specific PSA reference ranges, PSA density (PSAD), and percent free PSA (%fPSA). In this multicenter study, we compared these methods for their utility in cancer detection and their ability to predict pathologic stage after radical prostatectomy in patients with clinically localized, Stage T1c cancer.

Methods: Seven hundred seventy-three men (379 with prostate cancer, 394 with benign prostatic disease), 50 to 75 years old, from seven medical centers were enrolled in this prospective blinded study. All subjects had a palpably benign prostate, PSA 4.0 to 10.0 ng/mL, and a histologically confirmed diagnosis. Hybritech's Tandem PSA and free PSA assays were used.

Results: %fPSA and age-specific PSA cutoffs enhanced PSA specificity for cancer detection, but %fPSA maintained significantly higher sensitivities. Age-specific PSA cutoffs missed 20% to 60% of cancers in men older than 60 years of age. %fPSA and PSAD performed equally well for detection (95% sensitivity) if cutoffs of 25% fPSA or 0.078 PSAD were used. The commonly used PSAD cutoff of 0.15 detected only 59% of cancers. %fPSA and PSAD also produced similar results for prediction of the post-radical prostatectomy pathologic stage. Patients with cancer with higher %fPSA values (greater than 15%) or lower PSAD values (0.15 or less) tended to have less aggressive disease.

Conclusions: The results of this study demonstrated that cancer detection (sensitivity) is significantly higher with %fPSA than with age-specific PSA reference ranges. %fPSA and PSAD provide comparable results, suggesting that %fPSA may be used in place of PSAD for biopsy decisions and in algorithms for prediction of less aggressive tumors since the determination of %fPSA does not require ultrasound.