Clinical usefulness of free PSA in early detection of prostate cancer.
OBJECTIVE
Measurement of serum prostate-specific antigen (PSA) is widely used as an aid in early detection of prostate cancer. Most patients with prostate cancer and a PSA level less than 10.0 ng/ml have early-stage disease. Thus, the detection of prostate cancer in its potentially curable stages requires the use of low PSA cutoffs, inevitably leading to many unnecessary biopsies. The combined use of free PSA and total PSA increases specificity of early detection. To develop risk assessment guidelines and a cutoff value of ratio of free (f) to total (t) PSA with a high predictive value for prostate cancer in men to whom the test would be applied in real life practice, a multicenter early detection trial was initiated.


METHODS
In one week in November 1997, 963 urologists prospectively examined 11,644 men between 45 and 75 years by digital rectal examination (DRE) and prostate-specific antigen with 4.0 ng/ml as cutoff. Data of physical examination were collected by questionnaire. At this time participants were not aware of their PSA values. Suspicious findings were further investigated with sextant biopsy. Prostate volume was determined with transrectal ultrasound (TRUS). Different cutoff levels were correlated to age and detection rate.


RESULTS
From1,115 biopsied men, the data of 633 men fulfilled the criteria DRE-negative, TRUS-estimated volume, and PSA 4.0-10.0 ng/ml. In that cohort 91 cancers were detected. Percentage of fPSA was significantly more predictive of cancer than tPSA (p < 0.001). The area under the ROC curve was 0.72 for percent fPSA (% fPSA) and 0.62 for total PSA. The cancer risk nearly doubled using a cutoff of 10% fPSA, the median %PSA level of the detected cancers. A better discrimination of cancer and noncancer especially in the age group above 70 years is possible. Using a cutoff of 16% fPSA increases positive predictive value (PPV) to 25% missing only 4% of cancers. Nearly 45% of the biopsies could be avoided. In the age group 45-69 years, a cutoff of 20% fPSA leads to PPV of 15%, missing 6% of cancers. Unnecessary biopsies could be avoided in 12%.


CONCLUSIONS
Using % fPSA in early detection of prostate cancer reduces the number of unnecessary biopsies, especially in men with negative rectal examination in the PSA range of 4.0-10.0 ng/ml. In order to diminish biopsy rate in men 70 years or older a cutoff of 16% fPSA should be used. A cutoff of 20% fPSA in men younger than 70 years is recommended to increase sensitivity in that age group.
Luboldt
H J
HJ
Klinik und Poliklinik für Urologie, Kinderurologie und urologische Onkologie, Universitätsklinikum Essen, Gesamthochschule Essen, Essen. DrhLuboldt@aol.com
Swoboda
A
A
Börgermann
C
C
Fornara
P
P
Rübben
H
H
D000368:Aged; D001706:Biopsy; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000473:pathology
D017430:Prostate-Specific Antigen