Prostate Cancer PSA and Other Screening Tests
One of the best ways to detect prostate cancer early is through screening, which can help find some types of cancer at an early stage, when they may have a better prognosis. Since the prostate-specific antigen (PSA) test was introduced in the late 1980s, it has been commonly used in conjunction with a digital rectal exam to screen for prostate cancer.
What the PSA Test Measures
The PSA test is a blood test that measures a protein released in the blood by the prostate gland. Both normal and malignant (cancerous) prostate cells secrete the protein. While there is no perfect screening test for prostate cancer, PSA is the best indicator available. That said, abnormal PSA results alone are not sufficient to diagnose prostate cancer. Elevated PSA levels are most often caused by noncancerous conditions of the prostate, such as benign prostatic hyperplasia (BPH), and some men who have prostate cancer do not have elevated PSA.
The PSA test measures total PSA. The higher a man’s total PSA level, the more likely he is to have prostate cancer. Most doctors consider a total PSA level of 4.0 ng/mL or lower to be normal in men age 60 or older and 2.5 ng/mL or lower to be normal in men younger than 60. Total PSA is used not only to screen for prostate cancer but also to monitor patients who’ve had prostate cancer to check for recurrence.
Other Screening Tests
If your total PSA test results are high or abnormal, your doctor may use other screening tests, including special types of PSA tests or a PCA3 test, to help determine if you need a biopsy, which is the only way to definitively diagnose prostate cancer.
The free-PSA test checks for the amount of PSA in the blood that is not bound to other proteins. This is a subset of the total PSA. The test is usually ordered only if the total PSA is elevated. It can help your doctor determine whether you need further diagnostic tests. The free-PSA level is divided by the total PSA to get the percent of free PSA. A result of less than 10 percent means you have a higher risk for prostate cancer. The lower the percent, the higher the risk.
Prostate Health Index (PHI)
Approved by the U.S. Food and Drug Administration in 2012, the PHI is a blood test to detect and predict the probability of prostate cancer. It uses two of the PSA subset values to create a cancer risk ratio that may help your doctors determine whether they should perform a biopsy. Studies of the accuracy of this test are ongoing.
Urinary PCA3 Test
This is a urine test for proteins that are specific to prostate cancer. Unlike PSA, PCA3 is only produced by prostate cancer cells, and the level is not affected by prostate size. This test can be used in addition to total and free PSA tests to help determine whether a biopsy is needed. It is not used as a stand-alone test, and it is used more commonly in men who’ve had a negative biopsy (meaning cancer was not detected) to determine whether another biopsy may be warranted.
PSA Screening Risks & Benefits
In recent years, PSA screening has come under fire because of concerns that it has led to overdiagnosis and overtreatment. In fact, in 2012 the U.S. Preventive Services Task Force (USPSTF) recommended against routine PSA screening for prostate cancer because two studies did not show it substantially lowered death rates and because screening can result in harm from biopsies, from treatment of patients who may not be at risk of dying from prostate cancer, and from treatment-related side effects.1
At Seattle Cancer Care Alliance (SCCA), we believe there are several good reasons to continue PSA screening.
- It helps detect early-stage disease. PSA screening has yielded a dramatic transformation in how prostate cancer patients present; more present with early-stage and potentially curable disease.
- Screening and treatment can be done selectively, based on a man’s individual situation. PSA screening is a beneficial test that has likely saved many lives, but it also uncovers many cases of prostate cancer that do not need to be treated. The main harm in screening is not the PSA test itself but the possibility that the results may lead to overtreatment of low-risk cancers in older men. Men who are younger and appear to be healthy are most likely to benefit from screening that leads to early detection and treatment. Some low-risk prostate cancers can be carefully followed with active surveillance rather than treated initially with more aggressive measures.
- There are limitations to the USPSTF recommendation. The task force’s conclusion was based on studies that had limited follow-up and a lower death rate than expected in the absence of screening, which almost certainly understated the lives saved over the long term and produced an overly negative assessment of the screening benefit. In addition, the USPSTF overlooked several studies that reveal more substantial benefits for healthier, younger men.
- Screening works. Most importantly, there is no doubt that prostate cancer deaths have decreased by about 40 percent since the advent of PSA screening, as shown in a National Cancer Institute investigation.2
If you have any questions about whether the PSA test is right for you, talk with your doctor about the benefits and risks of PSA testing. The SCCA prostate cancer team is well equipped to discuss the potential benefits and risks of screening and whether regular screenings are appropriate for you.
AUA Guidelines for PSA Screening
In 2013, the American Urological Association (AUA) released PSA screening guidelines for various groups of men based on their age, health, and risk profile.3 SCCA’s prostate cancer specialists agree with the AUA’s guidelines, summarized here:
- Men under age 40: No PSA screening.
- Men 40 to 54 years old: No routine PSA screening.
- Men 55 to 69 years old: Talk with your doctor about the risks and benefits of PSA screening for you.
- Men age 70 or older: No routine PSA screening; however, if you are in excellent health, talk with your doctor about the risks and benefits of PSA screening for you.
- Men with less than a 10- to 15-year life expectancy: No routine PSA screening in men with poor health.
- Men at higher risk: Talk with your doctor about the risks and benefits of PSA screening for you.
1. Screening for Prostate Cancer, U.S. Preventive Services Task Force, released May 2012.
2. Hans Lilja et al, “Prediction of Significant Prostate Cancer Diagnosed 20 to 30 Years Later with a Single Measure of Prostate-Specific Antigen at or Before Age 50,” Cancer 117 (2011): 1210-1219, doi: 10.1002/cncr.25568.
3. Early Detection of Prostate Cancer: AUA Guidelines, American Urological Association, approved by AUA Board of Directors April 2013.