According to research from the National Cancer Institute (NCI), part of the National Institutes of Health, men who receive a reproducible prostate specific antigen (PSA) test result of 7 ng/ml (nanograms per milliliter) or greater are more likely to have a subsequent prostate biopsy compared to men with lower but still abnormal test results.
Men with a positive digital rectal exam (DRE) without a positive PSA test were less likely to receive biopsy than men with a positive PSA test. This research appears in the March 2005 Journal of Urology*.
National data on prostate biopsy rates following PSA or DRE screening are currently limited. These new findings, which contribute a good deal of information on the subject, are one of the initial results from the prostate component of NCI's ongoing multicenter Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. The PLCO is testing whether screening with PSA and DRE decreases prostate cancer mortality in men age 55 to 74.
Men in the screening arm of this randomized trial undergo PSA testing and DRE upon entry. They then have these tests annually for the next three years, and then have a PSA test without a DRE in years 4 and 5. This study looked at all men who had a positive PSA or DRE upon entry and men with positive post-entry results occurring by December 2000.
A total of 4,801 out of close to 40,000 men who were originally randomized to the screening arm of the PLCO had one abnormal prostate screening test upon entry, of whom 2,717 had abnormal PSAs. Diagnostic procedures, including biopsy, were looked at for a 3-year period following the first positive screening. Diagnostic follow-up in the United States was done at many sites across the country** and thus occurred beyond the control of the PLCO. However, the entry screening PSA test was done by one central laboratory at the University of California Los Angeles. The pattern of biopsies in PLCO men is thought to be representative of current clinical practice in response to a positive PSA or DRE in the years 1993 to 2001.
The results of a PSA test or DRE had a substantial impact on biopsy rates:
Men with PSAs greater than 4 ng/ml (considered positive in this study) upon entry into the PLCO had a biopsy rate over a 3-year period of 64 percent, while those with a positive DRE and PSA of 4ng/ml or less had a 27 percent biopsy rate.
Men with a baseline PSA greater than 10 ng/ml had a greater biopsy rate (85 percent) after 3 years than did men with baseline PSAs of 4 to 7 ng/ml (58 percent).
Among men first becoming PSA positive (greater than 4 ng/ml) after the study entry screen, those with PSA levels greater than 10 ng/ml were not more likely to receive a biopsy than men with PSAs of 4 to 7 ng/ml.
The study authors were able to identify various factors that affected biopsy rates:
Prior prostate biopsy, prior PSA tests, and a history of prostate problems were significantly associated with a lower biopsy rate only in men whose PSA was positive at entry.
In men with a positive DRE and negative PSA, a PSA value of 2.5 to 4.0 was associated with an increased biopsy rate compared to a result lower than 2.5.
Among men with a PSA test greater than 4, men with a positive DRE were about twice as likely to receive biopsy as men with a negative DRE.
Men often got repeat PSAs after the screening PSA. Those with repeat PSAs below 4 ng/ml had much lower biopsy rates than men with repeat PSAs greater than 4.
The men in this study and their physicians were aware that they were participating in a clinical trial and this fact may have affected their behavior in terms of diagnostic follow-up and biopsy. Nevertheless, the results of this study should be useful for calculating the cost of screening and for modeling how DRE and PSA tests are used in the general population.
According to lead author Paul F. Pinsky, Ph.D., NCI, "We can not yet answer the question of whether PSA tests and DRE have an effect on overall prostate cancer mortality, but these interim results give us a good indication that biopsy is more likely following a screening PSA of 7 ng/ml or greater that is reproducible in a large, geographically diverse sample of American men. These results suggest that PLCO is evaluating the effects of screening in a current and vigorous manner."
Posted by the National Cancer Institute
February 16, 2005
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