The PSA Test: Prostate Cancer Screening Explained

Prostate-specific antigen, or PSA, is a protein made by prostate cells. Both normal and cancerous prostate cells make it. The PSA test measures how much PSA is in your blood. Here is the catch. Prostate cancer and benign conditions can both raise PSA. An enlarged prostate (BPH) and inflammation (prostatitis) are common benign causes. That is a big reason the test is not a simple yes-or-no for cancer.

The test is used in three main ways. It monitors people already diagnosed with prostate cancer. It follows up on prostate symptoms. And, more controversially, it screens people who have no symptoms.

Not routinely. PSA was widely used for population screening from the late 1980s. As more was learned about its harms, many organizations began to caution against it. Today most recommend that anyone considering PSA screening first discuss the risks and benefits with their doctor.

The U.S. Preventive Services Task Force recommends:

• Ages 55–69: the decision to screen should be an individual one. Weigh the possible benefits and harms against your own values.
• Age 70 and older: PSA-based screening is not recommended.

Some organizations suggest earlier routine testing, at 40 or 45, for people at higher risk. That includes Black men, those with inherited BRCA2 changes (and to a lesser extent BRCA1), and those whose father or brother had prostate cancer.

No single cutoff separates normal from abnormal. No level means cancer for sure, though a higher PSA makes cancer more likely. A level above 4.0 ng/mL is generally considered abnormal and may lead to a biopsy. Doctors sometimes adjust the cutoff by age or medication. Temporary bumps can come from infection, inflammation, a recent biopsy, hard cycling, or ejaculation. So it is common to wait, and to avoid those activities before testing.

The possible benefit is catching prostate cancer earlier, when it may be easier to treat. That can lead to a small drop in prostate cancer deaths over about 10 years.

The harms are real and important.

• Overdiagnosis and overtreatment. Some cancers found by PSA grow so slowly they would never cause problems. Treating them can still cause urinary, bowel, and sexual side effects.
• Earlier detection does not always mean cure. Some tumors have already spread before they are found.
• False positives are common. About 6–7% of men have a false-positive PSA on a given screening round. Only about 25% of those biopsied for a high PSA turn out to have cancer. Biopsies also carry risks of pain, bleeding, and infection.

The USPSTF has put numbers on this. For every 1,000 men ages 55–69 screened for 13 years, roughly 1–2 prostate cancer deaths are avoided. About 240 have a positive result, many of them false. About 100 are diagnosed, and 80 are treated. Many of those treated have a serious complication, such as sexual dysfunction or urinary incontinence. This is exactly why NCI frames PSA screening as a personal decision, not an automatic one.

The PSA test is also valuable after treatment. Following surgery or radiation, a rising PSA can be the first sign of recurrence. It often appears months or years before symptoms. But one high reading does not mean the cancer is back. Doctors look for a rising trend over time, sometimes with imaging, before recommending more treatment.