Paul H. Lange

CONTEXT: The percentage of free prostate-specific antigen (PSA) in serum has been shown to enhance the specificity of PSA testing for prostate cancer detection, but earlier studies provided only preliminary cutoffs for clinical use. OBJECTIVE: To develop risk assessment guidelines and a cutoff value for defining abnormal percentage of free PSA in a population of men to whom the test would be applied. DESIGN: Prospective blinded study using the Tandem PSA and free PSA assays (Hybritech Inc, San Diego, Calif). SETTING: Seven nationwide university medical centers. PARTICIPANTS: A total of 773 men (379 with prostate cancer, 394 with benign prostatic disease) 50 to 75 years of age with a palpably benign prostate gland, PSA level of 4.0 to 10.0 ng/mL, and histologically confirmed diagnosis. MAIN OUTCOME MEASURES: A percentage of free PSA cutoff that maintained 95% sensitivity for prostate cancer detection, and probability of cancer for individual patients. RESULTS: The percentage of free PSA may be used in 2 ways: as a single cut-off (ie, perform a biopsy for all patients at or below a cutoff of 25% free PSA) or as an individual patient risk assessment (ie, base biopsy decisions on each patient's risk of cancer). The 25% free PSA cutoff detected 95% of cancers while avoiding 20% of unnecessary biopsies. The cancers associated with greater than 25% free PSA were more prevalent in older patients, and generally were less threatening in terms of tumor grade and volume. For individual patients, a lower percentage of free PSA was associated with a higher risk of cancer (range, 8%-56%). In the multivariate model used, the percentage of free PSA was an independent predictor of prostate cancer (odds ratio [OR], 3.2; 95% confidence interval [CI], 2.5-4.1; P < .001) and contributed significantly more than age (OR, 1.2; 95% CI, 0.92-1.55) or total PSA level (OR, 1.0; 95% CI, 0.92-1.11) in this cohort of subjects with total PSA values between 4.0 and 10.0 ng/mL. CONCLUSIONS: Use of the percentage of free PSA can reduce unnecessary biopsies in patients undergoing evaluation for prostate cancer, with a minimal loss in sensitivity in detecting cancer. A cutoff of 25% or less free PSA is recommended for patients with PSA values between 4.0 and 10.0 ng/mL and a palpably benign gland, regardless of patient age or prostate size. To our knowledge, this study is the largest series to date evaluating the percentage of free PSA in a population representative of patients in whom the test would be used in clinical practice.

In the late 1980s and early 1990s, the number of newly diagnosed prostate cancers in the United States increased dramatically, surpassing lung cancer as the most common cancer in men. For example, the percentage of patients with low-risk disease has increased (45.3% in 1999-2001 vs. 29.8% in 1989-1992; P < .0001). In 2009, an estimated 192,280 new cases were diagnosed and prostate cancer was expected to account for 25% of new cancer cases in men. 1 Fortunately, the age-adjusted death rates from prostate cancer have also declined (-4.1% annually from 1994 to 2001).

Prostate specific antigen (PSA), neutral serine protease secreted exclusively by prostatic epithelial cells, has a number of applications in the management of men with prostatic carcinoma. While it is widely recognized that elevated PSA correlates with the presence of carcinoma, little data exist regarding the use of PSA as the initial test in the early detection of prostatic cancer. We measured serum PSA levels in men older than 50 years and performed digital rectal examination and ultrasound guided prostate biopsy of those who had a PSA level of greater than 4.0 ng./ml. A total of 1,249 men entered the protocol, of whom 187 (15.0%) had PSA levels above 4.0 ng./ml. Digital rectal examination and ultrasound guided biopsy were performed at our facility in 105 patients (56.2%). A total of 32 carcinomas (30.5%) was detected, including 23 in men with PSA between 4.1 and 10.0 ng./ml. and 9 in men with a PSA of greater than 10.0 ng./ml. Of the 32 carcinomas 12 (37.5%) occurred in men with normal prostates or glands demonstrating only asymmetry on digital rectal examination, and 3 men had carcinoma despite normal digital rectal examination and no hypoechoic peripheral zone lesion detected on ultrasound. Of the 32 patients 30 had clinically localized carcinoma but 7 of the 16 undergoing radical prostatectomy had pathological upstaging. We conclude that PSA represents an important adjunct to digital rectal examination for the early detection of prostatic carcinoma. The efficacy of this or any other early detection test to decrease prostate cancer mortality necessitates the results of prospectively randomized clinical trials.

We evaluated serum prostate specific antigen before and after radical prostatectomy. In 100 consecutive patients who underwent radical prostatectomy, preoperative prostate specific antigen levels tended to increase with the increasing severity of pathological stage. However, even at levels of greater than 10 ng. per ml. the positive and negative predictive values (78 and 61 per cent, respectively) of prostate specific antigen to predict extracapsular disease were not sufficient to make this test useful alone for staging. In theory, after radical prostatectomy prostate specific antigen should be zero if no remaining prostatic tissue is present. Tests of precision and analytical sensitivity in our laboratory using a commercial prostate specific antigen assay revealed that a value of 0.4 ng. per ml. or more is different from zero at a greater than 95 per cent confidence level. With this guideline we evaluated the meaning of prostate specific antigen levels 3 to 6 months after radical prostatectomy in 59 men. Among men whose prostate specific antigen level was less than 0.4 ng. per ml. only 9 per cent demonstrated recurrence as evidenced by the development of positive bone scan or progressively elevated prostate specific antigen levels within 6 to 50 months. Alternatively, in men whose 3 to 6-month prostate specific antigen level was 0.4 ng per ml. or more there was evidence of recurrence in 100 per cent within 6 to 49 months (p less than 0.0001). Progressively elevated (more than 0.4 ng. per ml.) prostate specific antigen levels preceded recurrence from 12 to 43 months in all 6 patients who had positive bone scans, while increasing prostate specific antigen levels since radical prostatectomy have continued from 9 to 65 months in the 11 patients who have no radiological evidence of recurrent disease to date. Prostatic acid phosphatase serum values after radical prostatectomy were not useful to predict persistent disease. Prostate specific antigen values 3 to 6 months after radical prostatectomy are a sensitive indicator of persistent disease after radical prostatectomy and often precede other evidence of this occurrence by many years. This fact may alter concepts about surgical results, and possibly shorten and sharpen clinical studies involving adjuvant therapy after radical prostatectomy.