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 < or =2.5 ng/mL.


METHODS
Between 1999 and 2006, 543 men with a PSA < or =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 < .001) and rectal examination findings (P = .001) were the only independent predictors of prostate cancer. The combined AUC of all predictors (0.69) was not significantly (P = .7) higher than that of percentage of free PSA alone (0.68).


CONCLUSIONS
The risk of prostate cancer is clearly non-negligible in patients with PSA < or =2.5 ng/mL. The percent free PSA can accurately predict the prevalence of prostate cancer at prostate biopsy in these individuals.
Cancer Prognostics and Health Outcomes Unit, University of Montreal, Montreal, Quebec, Canada. walzj@marseille.fnclcc.fr
Jochen
J
Walz
Alexander
A
Haese
Vincenzo
V
Scattoni
Thomas
T
Steuber
Felix K H
FK
Chun
Alberto
A
Briganti
Francesco
F
Montorsi
Markus
M
Graefen
Hartwig
H
Huland
Pierre I
PI
Karakiewicz
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D014408:Biomarkers, Tumor / Q000097:blood*; D051517:Digital Rectal Examination; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood*; D012372:ROC Curve; D012306:Risk
D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen