PSA Testing for Prostate Cancer

(RxWiki News) The prostate-specific antigen (PSA) blood test is approved for prostate cancer detection. It is widely used to screen men for the disease. Early prostate cancer usually causes no symptoms but often produces a rise in PSA. This rise offers a clue that more testing may detect a malignant tumor.

The PSA test can detect prostate tumors at an early stage, when they respond best to treatment. But for much of the past decade, men have received mixed messages about who should have this test. That’s because routine screening can lead to over-diagnosis of non-life-threatening cancers for which treatment is not necessary.

The latest advice is men age 55 to 69 to make an individual decision about whether to have a PSA screening after discussing the pros and cons with their doctors. 

If you’re thinking about getting screening, here are six key questions to ask yourself and discuss with your doctor. The answers can help decide whether screening is right for you.

  • How high is my risk?
  • Am I willing to undergo a biopsy if my test comes back positive?
  • How would I feel if the biopsy revealed that my results were false-positive, which would mean that I had a procedure I didn’t need?
  • Do I want to learn that I have prostate cancer even if it might be slow-growing and perhaps never cause harm?
  • Would I be willing to forgo immediate treatment and choose active surveillance instead?
  • How would I feel if I get prostate cancer after choosing not to be tested?

The test measures an enzyme produced by a type of cell in the prostate. It is secreted during ejaculation into the prostatic ducts that empty into the urethra. PSA liquefies semen after ejaculation, promoting the release of sperm. Only very small amounts of PSA are present in the blood. But an abnormality of the prostate can disrupt the gland and create an opening for PSA to pass into the bloodstream. Thus, high blood levels of PSA can be a sign of prostate problems, including cancer.

Clinical studies have shown the following benefits of PSA testing:

  • A high PSA is the single best predictor of prostate cancer.
  • PSA testing detects prostate cancer about five to 10 years earlier than digital rectal examinations (DREs).
  • Most cancers detected with PSA testing are curable.
  • Regular PSA testing nearly eliminates the diagnosis of advanced prostate cancer.
  • A baseline PSA test in men in their 40s or 50s can help predict the risk of prostate cancer up to 25 years later.

The trade-off of routine screening is the over-diagnosis of non-life-threatening cancers for which treatment is not necessary. This occurs more often in older men, who have less to gain from screening because of a shorter life expectancy.

  • Another drawback of PSA testing is that most men with a high PSA do not have prostate cancer.
  • Instead, BPH (benign prostatic hyperplasia) or inflammation is to blame. BPH is also known as benign prostatic enlargement (BPE).
  • These men may have unnecessary diagnostic tests and treatments, which can lead to undue anxiety.
  • Men should discuss both the benefits and limitations of PSA testing with their physician before having their PSA levels measured.

The likelihood of having prostate cancer varies according to PSA level and if the digital rectal exam (DRE) is normal. The risk increases as PSA rises and is higher if the DRE is abnormal.

The risks of finding prostate cancer on a biopsy in men who have a normal DRE are as follows:

  • PSA 0 to 2 ng/mL has a 12% risk.
  • PSA 2 to 4 ng/mL has a 15% to 25% risk.
  • PSA 4 to 10 ng/mL has a 17% to 32% risk.
  • PSA 10 to 20 ng/mL has a 50% to 75% risk.
  • PSA higher than 20 ng/mL has a 90% risk.

There is no PSA level below which physicians can reassure a man that he does not have prostate cancer. Therefore, it is not possible to define a “normal” level. Yet, most doctors would consider a PSA above 3 ng/mL to 4 ng/mL in men between 50 to 70 years of age to be a reason for further evaluation, especially if it is rising.

  • Most experts agree that PSA screening should be used in conjunction with other information (family history, race, and age) to assess the overall likelihood that prostate cancer is present.
  • It should be performed following a discussion with the patient about its benefits and risks.

Experts agree that there is harm with widespread PSA screening. But if there was screening focused on those at greatest risk of prostate cancer, and active surveillance for those who don’t need immediate treatment, then a shift in the balance of benefit and harm toward benefit could occur.

Several factors may affect the results of a PSA test.

  • Some studies show that ejaculation one or two days before a PSA test may increase PSA levels in the blood.
  • Men should abstain from sex for 72 hours prior to a PSA test.
  • DREs and biopsies of the prostate may also affect PSA levels. The increase in PSA caused by a DRE is not believed to be significant enough to produce a false-positive test result in most men. A prostate biopsy, however, may elevate PSA levels for four weeks or longer.

Other prostate problems also can inflate PSA levels, including:

  • BPH
  • Prostatitis

BPH medications including 5-alpha reductase inhibitors (ARIs) can lower PSA levels by about 50%. This drug-related reduction in PSA level must be considered to avoid misinterpretation of the test result.