Are Annual Prostate Cancer Screenings Necessary?

By Krystle Seu, Maushami DeSoto, Ph.D. and Dana Casciotti, Ph.D.

Updated October 2011

Prostate cancer is the #1 cancer in men and the second leading cause of cancer deaths for men in the United States, after lung cancer [1].  One in every six men will be diagnosed with prostate cancer in his lifetime [2], with about 90% of cases occurring in men 55 and older, and 71% of deaths occurring in men 75 and older [3].  For these reasons, annual screenings would seem to be an important way to prevent prostate cancer.  But there is a hot debate within the medical community: do regular prostate cancer screenings do more harm than good?

In October 2011, the U.S. Preventive Services Task Force issued new draft recommendations which stated that PSA tests should not be recommended for men of any age if they do not have any symptoms of prostate cancer [4]. The Task Force is an independent group of medical professionals that reviews all evidence on preventive health care services, such as screening.

The reason why screening may not be necessary is that prostate cancer grows very slowly.  Even without treatment, many men with prostate cancer will live with the disease until they eventually die of some other, unrelated cause.

Prostate cancer occurs when cells create small tumors in the prostate gland, which is an important part of the male reproductive system.  Screening can be performed quickly and easily in a physician’s office using two tests: the prostate-specific-antigen (PSA) blood test, and the digital rectal exam (DRE), a manual exam of the prostate area.

Most screening tests are not 100% accurate, but these prostate tests are especially inaccurate.  Most men with a high PSA level (>4ng/mL) do not have prostate cancer (this is known as a false positive), and some men with prostate cancer have a low PSA level (this is called a false negative).  The DRE also results in many false positives and false negatives.  Using both screening methods together will miss fewer cancers but also increases the number of false positives, which can lead to more testing (usually biopsies of the prostate) and possibly result in medical complications. A biopsy to determine if there is a cancerous growth in the prostate involves inserting a needle-usually through the rectum-to remove a small sample of prostate tissue.

Inaccurate results are not the only problem. Even if a man has prostate cancer, if he does not have symptoms he may not need to be treated. Experts estimate that between 18% and 85% of prostate cancers detected by these screening tests would never become advanced enough to harm the patient.  This wide range of uncertainty, however (is it less than 1 out of 5 or more than 4 out of 5?) just adds to the confusion.

Complications from prostate cancer screening can be harmful and expensive, and the treatments for prostate cancer often cause serious and long-lasting problems, such as urinary incontinence and impotence [5].  Since the disease is rarely fatal, many doctors and patients question whether annual prostate cancer screenings (or the treatment that is recommended following diagnosis) are a good idea.

New Research Findings

Major research studies such as the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial and the European Randomized Trial of Screening for Prostate Cancer (ERSPC) have tried to shed light on the risks and benefits of regular screening.  The PLCO studied 76,000 men for 7-10 years and found that the death rate from prostate cancer was low, and that it did not differ between the men who were screened every year for the first six years of the study and those who received their usual care (which ranged from no screening to occasional screening) [6].  For most of the patients, “usual care” included at least one screening during the first seven years of the study.

The European study included 182,000 men, ranging from 50 to 74 years old, from seven different European countries [6].  The researchers found that PSA screening every four years without DRE reduces prostate cancer deaths by about 20%. However, for each death prevented, the program needed to screen more than 1,400 men and treat an additional 48 men [7].

Researchers are also trying to determine if other types of PSA testing might be more accurate in detecting prostate cancer, such as changes in PSA levels when a man has multiple tests over time.  The rate of change of PSA level from one test to the next is known as “PSA velocity.”

One study examined if PSA velocity could improve cancer detection compared to standard PSA and DRE screening tests [8].  Because men with high PSA levels and positive DRE results typically undergo prostate biopsies to determine the presence of cancer, this study evaluated if PSA velocity helped detect cancer in men with low PSA and negative DRE results.  Over 5,500 men were included in the study and men with high PSA velocity-almost 1 in 7 men-were biopsied.  The researchers found that doing biopsies on the basis of high PSA velocity in the absence of a high PSA or positive DRE would lead to a large number of biopsies but would not improve cancer detection [8].

Does Screening Improve Survival?

A study published in 2011 by Swedish researcher Gabriel Sandblom and his colleagues followed men for 20 years to determine if screening for prostate cancer reduced deaths from prostate cancer.  Investigators enrolled 9,026 men in Norrkoping, Sweden, aged 50-69 in 1987.  They randomly chose 1,494 men to undergo screening every 3 years, using the DRE in 1987 and 1990 and DRE and PSA in 1993 and 1996.  They were compared to 7,532 men who were not screened.

As of December 1999, 4% (292) of men in the control group and 6% (85) of men in the screening group were diagnosed with prostate cancer.  Interestingly, among the 85 men diagnosed with cancer in the screened group, only about half of those cancers (43) were diagnosed at screening.  The other 42 cancers were “interval cancers,” or diagnosed between screening appointments.  The relatively small difference in diagnosis between the screened and non-screened groups, and the fact that only half of that difference (1%) was a result of screening, suggests that prostate cancer screening is not very effective.  In addition, since prostate cancer grows slowly, many of those cancers could have been caught without screening before they were dangerous

Did the men who were screened live longer as a result of screening?  The researchers concluded that there was no significant difference in overall survival for men diagnosed with prostate cancer that were screened or not screened.  Overall, 81% of men with prostate cancer in the screened group (69/85) and 86% of men with prostate cancer in the non-screened comparison group (252/292) died during the study period.  About half of those men did not die of prostate cancer.  Only 35% of men in the screened group (30/85) and 45% of men in the comparison group (130/292) died of prostate cancer.  The difference was not statistically significant, which means the difference could be due to chance.  However, if the 35% vs. 45% difference was maintained in a larger sample of men, that difference would have been statistically significant.  Research using a much larger sample would be needed to determine if screening did make a significant difference in reducing deaths from prostate cancer.   Based on this study, screening did not significantly reduce deaths from prostate cancer.

The study was stopped at the end of 1999, and unfortunately more recent follow-up data are not available.

What Should Men Do?

In spite of these important studies, we still do not have clear answers about which men, if any, should be screened and how often.

The benefit of screening is that the disease is often curable with early detection (90% or better).  Common treatments like surgery or radiation aim to remove or kill all cancerous cells in the prostate.  If the cancer spreads beyond the prostate before it is treated, it is often fatal.  However, the cancer usually grows so slowly that is often equally safe to wait until there are symptoms before attempting to diagnose prostate cancer.  Symptoms of prostate cancer might include urinary problems, difficulty having an erection, or blood in the urine or semen [9].

To reduce the risks of over-treatment, doctors and scientists are searching for better tests for prostate cancer detection.

Family history of prostate cancer or other cancers should influence how often a man chooses to get PSA screening.  However, the studies described above indicate that it is unlikely that annual screenings for all men are a good idea.  What about less frequent screening?

In 2009, the U.S. Preventive Services Task Force stated that prostate cancer screening is not recommended for men over 75, and concluded that the current evidence is not sufficient to determine “the balance of benefits and harms of prostate cancer screening in men younger than age 75 years” [10]. In April 2009, the American Urological Association issued new guidelines saying that annual screening was no longer recommended.

The U.S. Preventive Services Task Force went even further in their draft recommendations in October 2011, concluding that PSA tests should not be recommended for men of any age unless they have symptoms of possible prostate cancer. However, the Task Force made it clear that there was little evidence to support the recommendation against screening, even if they believe that there is more evidence against PSA screening than for it.

References:

  1. United States Cancer Statistics (2005). Center for Disease Control and Prevention. Retrieved on April 13, 2009 from: http://www.cdc.gov/Features/CancerStatistics/
  2. Prostate Cancer Foundation. Risk Factors. Retrieved on April 17, 2009 from: http://www.prostatecancerfoundation.org/site/c.itIWK2OSG/b.70619/k.446E/Risk_Factors.htm
  3. National Cancer Institute (2009). SEER fact sheet. Retrieved on April 13, 2009 from: http://seer.cancer.gov/statfacts/html/prost.html
  4. Agency for Health Care Research Quality. US Preventive Task Force. Screening for Prostate Cancer DRAFT. Retrieved on October 7, 2011 http://www.uspreventiveservicestaskforce.org/uspstf12/prostate/draftrecprostate.htm
  5. Sanda MG, Dunn RL, Michalski J, et al. Quality of life and satisfaction with outcome among prostate-cancer survivors. N Engl J Med. 2008;358(12):1250-1261.
  6. Andriole GL, Crawford ED, Grubb RL III, et al. (2009). Mortality results from a randomized prostate-cancer screening trial. New England Journal of Medicine, 360, 13:1310-1319.
  7. Schroder, F. H. et al. (2009). Screening and prostate-cancer mortality in a randomized European study. New England Journal of Medicine, 360, 13: 1320-1328.
  8. Vickers AJ, Till C, Tangen CM, et al. (2011).  An Empirical Evaluation of Guidelines on Prostate-specific Antigen Velocity in Prostate Cancer Detection. J Natl Cancer Inst. Feb 24 [Epub ahead of print]
  9. National Cancer Institute. U.S. Institutes of Health. What You Need to Know About Prostate Cancer. Retrieved on March 2, 2011 from: http://www.cancer.gov/cancertopics/wyntk/prostate
  10. Agency for Health Care Research Quality. US Preventive Task Force. Screening for Prostate Cancer. Retrieved on April 17, 2009 from: http://www.uspreventiveservicestaskforce.org/uspstf/uspsprca.htm
  11. American Urological Association Education and Research, Inc.  Prostate-Specific Antigen Best Practice Statement: 2009 Update.  Retrieved July 7, 2011 from : http://www.auanet.org/content/guidelines-and-quality-care/clinical-guidelines/main-reports/psa09.pdf

More Information:

National Cancer Institute. U.S. Institutes of Health. Prostate Cancer. Retrieved on April 17, 2009 from: http://www.cancer.gov/cancertopics/types/prostate

National Cancer Institute, Division of Cancer Prevention. (2009). Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. Retrieved on April 13, 2009 from: http://prevention.cancer.gov/plco

Barry MJ. (2009). Screening for Prostate Cancer-The Controversy that Refuses to Die. Editorial. New England Journal of Medicine, 360. 13: 1351-1354.