Can PSA diagnose and stage prostate cancer?

This page tells you about how PSA is used in diagnosing and staging prostate cancer.

PSA stands for prostate specific antigen. It is a chemical made by prostate gland cells and secreted into the blood. When the prostate gets enlarged, the level of this marker in the blood goes up because there are more prostate cells to make PSA and it is more likely to leak into the bloodstream. The prostate tends to grow as men get older. This is called benign enlargement of the prostate.

Cancerous prostate cells also make PSA, so the level of PSA in the blood goes up in prostate cancer as well as in benign enlargement of the prostate. The level of PSA also goes up in some other conditions such as inflammation of the prostate (prostatitis), which may be caused by an infection.

The normal level of PSA varies from one person to another. So it is not possible to quote a level that means normal for everyone. But doctors usually take a level under about 4 as normal. A level between 4 and 10 usually indicates a benign enlarged prostate that is not cancerous. But in a small number of cases, it may be a sign of early prostate cancer. A level between 10 and 40 gives a 40% chance of having prostate cancer.

PSA cannot tell us the stage of prostate cancer. It can indicate that the prostate may be enlarged. And if the PSA levels are very high there is a greater chance that a prostate cancer has spread.

The PSA test on its own is not a reliable test for cancer. Because there is no absolute normal, it is not really possible to judge what level indicates cancer. 2 out of every 3 men found to have a raised PSA don't have cancer. And some men with prostate cancer don't have a raised PSA.

To diagnose prostate cancer, doctors combine a PSA blood test with a rectal examination. You may also have an ultrasound scan. But you can only really get a definite diagnosis by taking a tissue sample (biopsy).

As well as being used to help diagnose prostate cancer, the PSA test is also used to monitor your progress after treatment.

You could have a look at the prostate cancer section in CancerHelp UK. There is a lot more information about prostate cancer and its treatment.