PSA stands for prostate specific antigen. PSA is as enzyme produced by the epithelial cells of the prostate gland and secreted into semen. Its physiological function is to liquefy semen and dissolve cervical mucus so that sperm can reach and fertilize an egg in the uterus. PSA is normally found in the serum of males, and can be abnormally elevated in several prostate disorders. Physicians have used elevated serum PSA levels as a marker to screen for prostate cancer. Recently, the United States Preventative Services Task Force (USPSTF) has recommended against using the PSA test to screen men for prostate cancer. The USPSTF wrote, “the potential benefit does not outweigh the expected harms”. In addition, they cited a high false positive rate, overdiagnosis, and overtreatment of prostate cancer as a result of the PSA screening test as reasons for the recommendation.
This stance has been controversial.
Many medical groups have agreed with the recommendation, but many others have disagreed with it.
Researchers, lead by Dr. Edward Messing of the University of Rochester in New York, have found that elimination of the PSA prostate cancer screening test would triple the number of men diagnosed with advanced metastatic prostate cancer. The results of their study were published online in the journal Cancer. The investigators computed the total number of men who presented with metastatic prostate cancer in the Surveillance, Epidemiology, and End Results (SEER) registry. The investigators also used a retrospective review to estimate the number of metastatic prostate cancer cases that would be expected to occur in the absence of PSA testing. The investigators found that there would be an additional 17,000 cases of metastatic prostate cancer diagnosed without the use of PSA testing in the year 2008.
The authors wrote, “the objective of this study was to compare the risk of presenting with [metastatic prostate cancer] under the current screening practices versus no screening using historic data from the SEER database… Our analyses suggest that, if the pre- PSA era incidence rates were present in the modern US population, then the total number of men presenting with [metastatic prostate cancer] would be approximately 3 times greater than the number actually observed. We believe that these estimates must be taken into consideration (bearing in mind the limitations of observational data) when public health policy-level recommendations are made regarding PSA screening”.
To make things more difficult, several studies have disagreed as to whether there is a mortality benefit from PSA screening. This leaves us in a conundrum. Do we use the PSA test to screen for prostate cancer or do we not use it? The best approach is to have an educated discussion with our patients. We must discuss the benefits and disadvantages of the PSA test. Patients should know that there is a chance for false positives, and that a positive result will require additional tests that may have complications. In addition, we should discuss the slow growing nature of prostate cancer with our patients. Finally, we should discuss complications that can result from treatment of prostate cancer which include erectile dysfunction and urinary incontinence, as well as others. In the end, the educated patient, in discussion with their physician, should make the decision to use the PSA test as a screening modality for prostate cancer.
Emil Scosyrev et al. “Prostate-specific antigen screening for prostate cancer and the risk of overt metastatic disease at presentation” Cancer published online July 30, 2012 DOI: 10.1002/cncr.27503