Robustness of free prostate specific antigen measurements to reduce unnecessary biopsies in the 2.6 to 4.0 ng./ml. range.
OBJECTIVE
Prostate specific antigen (PSA) cutoffs lower than 4.0 ng./ml. are being evaluated more frequently but lower PSA cutoffs increase the number of prostatic biopsies. PSA exists in several forms free and complexed to proteins. Percent free PSA is lower in men with prostate cancer. Accordingly, free PSA and complexed PSA have been used to distinguish between cancer and benign disease in the diagnostic gray zone of 4 to 10 ng./ml. to eliminate unnecessary biopsies. There are limited data on the robustness of free PSA measurements in the 2.6 to 4.0 ng./ml. total PSA range.


METHODS
We evaluated percent free PSA measurements to discriminate between cancer and benign conditions in 965 consecutive volunteers in a prostate cancer screening study who underwent prostatic biopsy for a PSA of 2.6 to 4.0 ng./ml. and had benign digital rectal examination.


RESULTS
Overall 25% of men had cancer detected. A 25% free PSA cutoff detected 85% of cancers and avoided 19% of negative (cancer-free) biopsies, while a 30% free PSA cutoff detected 93% of cancers and avoided only 9% of negative biopsies. Of those men who underwent radical prostatectomy 132 (80%) had pathologically organ confined tumors. Only 5% of these tumors fulfilled the published pathological criteria for possibly clinically unimportant tumors.


CONCLUSIONS
Percent free PSA provides risk assessment but does not eliminate many unnecessary prostatic biopsies while maintaining a high sensitivity in the narrow total PSA range of 2.6 to 4.0 ng./ml.
Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.
Kimberly A
KA
Roehl
Jo Ann V
JA
Antenor
William J
WJ
Catalona
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001707:Biopsy, Needle / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000473:pathology*; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D019564:Unnecessary Procedures
D017430:Prostate-Specific Antigen