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Evidence Summary

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PSA screening may or may not reduce deaths due to prostate cancer. Harms include false-positive results, unnecessary biopsies, and overdiagnosis.

Fenton JJ, Weyrich MS, Durbin S, et al. Prostate-Specific Antigen-Based Screening for Prostate Cancer: Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA. 2018;319:1914-31.

Review question

What are the benefits and harms of screening men for prostate cancer using the prostate-specific antigen (PSA) test?

Background

Prostate cancer is one of the most commonly diagnosed cancers in men. Many prostate cancers are slow-growing and are not life-threatening. The PSA test is a blood test used to screen for prostate cancer. It can help detect prostate cancer at an early stage when it may be easier to treat. However, men with a positive PSA test may have a prostate condition other than cancer (false-positive test) or prostate cancer that is unlikely to progress and doesn’t need to be treated (overdiagnosis). Men with positive screening tests often have further, more invasive tests, such as prostate biopsy. These tests can have complications.

How the review was done

Researchers in the USA did a systematic review of studies available up to February 2018. They found 8 studies assessing PSA screening, including 3 randomized controlled trials (RCTs) with 647,906 men who were between 50 and 74 years of age.

The key features of the RCTs were:

  • men didn’t have symptoms before screening; and
  • screening was compared with no screening.

What the researchers found

Compared with no screening, PSA screening:

  • reduced death due to prostate cancer in 1 trial but not in 2 other trials; and
  • had no effect on death due to any cause.

No prostate cancer was found in 10% to 18% of men who had a positive PSA test. In men who had a biopsy after a positive PSA test, 61% to 76% did not have prostate cancer.

Interpretation

Why do the 3 trials show different results for reducing death due to prostate cancer?

Differences within the trials may have affected the results. For example, some trials did PSA tests every year and some every 2 to 4 years. Trials also used different levels of PSA to indicate the need for a biopsy. If a lower PSA cutpoint was used, the PSA test would be positive for more people than if a higher PSA cutpoint was used. Some of the trials had problems: Some men in the no-screening groups had a PSA test done when they shouldn’t have (contamination), and some men who were supposed to have a PSA test done did not (poor adherence).

Conclusions

In men without symptoms of prostate cancer, PSA screening may or may not reduce prostate cancer mortality. Harms of PSA screening include false-positive test results, unnecessary biopsies, and overdiagnosis.

PSA screening vs no screening in men without prostate cancer symptoms*

Outcomes

Number of trials (number of men)

Effects of screening

Death due to any cause

3 trials (647,751 men)

No benefit at 10 to 15 years of follow-up.

Death due to prostate cancer

1 trial (162,243 men)

0.5% of men screened and 0.6% of men not screened died of prostate cancer over 13 years. This means about 12 fewer men out of 10,000 died of prostate cancer over 13 years because they had a PSA test done.

 

2 trials (485,508 men)

No benefit at 10 to 15 years of follow-up.

False-positive PSA test result

2 trials (94,180 men)

10% to 18% of men who were screened had a positive PSA test result, but no prostate cancer was found.

 

3 trials (647,906 men)

61% to 76% of men who had a biopsy after a positive PSA test did not have prostate cancer.

Overdiagnosis

2 trials (238,926 men)

21% to 50% of prostate cancers that were detected by PSA screening were not important to find because they were unlikely to cause symptoms or death.

PSA = prostate-specific antigen.

*Based on results of randomized controlled trials.




Glossary

False-positive
A test result that suggests the presence of a disease which turns out not to be there.
Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.

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    Canadian Task Force on Preventive Health Care
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  • Breast cancer: Patient algorithm

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    The Canadian Task Force on Preventive Health Care recommends women between 50 and 74 years old who are not at high risk get screened for breast cancer every 2 to 3 years. Talk to your doctor about screening options if you are at high risk or over 74 years old.
  • Breast cancer: Patient FAQ

    Canadian Task Force on Preventive Health Care
    This resource includes frequently asked questions about breast cancer, including: Who is considered high risk? What are the harms associated with mammography? and Why is routine screening NOT recommended for women 40-49 years?
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