Screening with prostate specific antigen (PSA) blood testing is used by more than 60% of men over age 50. Despite this, controversy swirls around its use for this purpose, stemming from disagreements on whether and by how much it truly benefits men with regard to prostate cancer, and because of the major consequences, both physically and economically, of diagnostic work-ups and treatment for those who are screened. Two huge randomized trials were conducted with the hope that their results would resolve the issue one way or the other, but their recent publication has done little to quell the concerns and opinions of those on either side. We present pro and con articles to outline key issues on each side of this debate.
E. David Crawford, M.D
Professor of Surgery, Urology & Radiation Oncology
Head, Section of Urologic Oncology,
University of Colorado Health Sciences Center Denver
Paul Maroni, M.D.
Assistant Professor
Department of Surgery (Urology)
Anschutz Cancer Center
University of Colorado Denver
This past March, early results from the two large ongoing, government-sponsored prostate cancer screening studies were published in the New England Journal of Medicine. These two articles were the focus of intense media attention. The US-sponsored Prostate, Lung, Colorectal, and Ovarian (PLCO) Trial and European Randomized Study of Screening for Prostate Cancer (ERSPC) cast a thick cloud of doubt over the usefulness of the PSA blood test and rectal exams in the early detection of prostate cancer (1,2).
The PLCO study showed no benefit to screening up to seven to 10 years and the other European trial showed only a small benefit at 9 years. These trials clearly highlighted a few important issues: 1) less than 1% of men die from prostate cancer over a 10-year period of time, 2) many men need to be tested (over 1,000) to prevent one death from prostate cancer, and 3) when cancer is found, many men need to be treated (around 50) to prevent one death from prostate cancer.
So, if it is not that threatening and not much can apparently be done to prevent death from prostate cancer, why should we bother to look for it?
We believe that there are many valid arguments for continuing to screen men for prostate cancer. Since prostate screening became more widespread in the late 1980s there has been a very clear decrease in the number of men diagnosed with metastatic, advanced cancer and there has been a decrease in the number of prostate cancer deaths. Around 40,000 US men died each year from prostate cancer in the early 1990s compared to about 27,000 men dying now (3).
This 30 percent reduction in deaths from prostate cancer occurred over a period of time when the total U.S. population increased by about 20 percent, signifying an important decrease in cancer-related death that has occurred in no other cancer type. While this could also be attributed to better treatments for cancer, the relationship to when prostate cancer screening became more widespread is compelling.
Another important point to keep in mind is that prostate cancer is exceptionally slow-growing in most cases. Screening has been estimated to detect prostate cancer about 5 years before a man would experience symptoms from his cancer (4). Generally, when symptoms are present, cure from prostate cancer is much less likely, but men will usually still live another 3 to 8 years. This means that both PLCO and ERSPC are still too short to detect a meaningful difference in a cancer that takes a decade or more to cause death. We expect that both of these studies will reveal the important benefits of prostate screening when patients have been followed for 15 or more years. Those results are still many years away, so we should not become lax in screening until these studies are truly finished. Both trials support the concept that men with a less than 10-year life expectancy may not benefit from routine screening.
The highly regarded US Preventive Services Task Force, which makes evidence-based judgments about all types of screening tests for disease prevention, has never endorsed prostate screening and has recommended no screening in men over 75 years old. We also need to be able to distinguish the truly threatening cancers from the slow-growing cancers that rarely cause problems. Only about one in six men diagnosed with prostate cancer will ultimately die from it. This percentage is the lowest among all solid organ cancers. For instance, lung cancer kills roughly four out of five and colon cancer kills two out of five. Patients should be presented with the real risks from their cancer as well as their other medical problems. They would in some cases be surprised to hear that their risks from high blood pressure, diabetes, and heart disease are worse than their risk of dying from cancer. In men that do not have threatening cancers, a stronger push by clinicians needs to be made for watchful waiting, studies aimed at slowing the growth of the cancer, and less invasive treatments aimed at reducing side effects and cost.
People have highlighted a need for more accurate tests. There is no question that these would be helpful to prevent unnecessary testing and potentially reduce the costs of screening. One must understand that the development of these new tests takes a very long time. They would then need to be tested in a manner similar to the PLCO and ERSPC studies over many years. We should not abandon a test that, while imperfect, is helpful in detecting early prostate cancer and will ultimately be shown to meaningfully prevent death.
REFERENCES:
- Andriole GL, Crawford ED, Grubb III RL, et al. Mortality results from a randomized prostate-cancer screening trial. NEJM 360:1310, 2009.
- Schröder FH, Hugosson J, Roobol MJ, et al. Screening and prostate-cancer mortality in a randomized European study. NEJM 360:1320, 2009.
- American Cancer Society. Cancer facts and figures 2009. Atlanta: American Cancer Society; 2009.
- Telesca D, Etzioni R, and Gulati R. Estimating lead time and overdiagnosis associated with PSA screening from prostate cancer incidence trends. Biometrics 64:10, 2008.
