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You likely already know that PSA can be a sign of prostate cancer. PSA stands for "prostate-specific antigen."

Most prostate cells produce PSA. More PSA enters your bloodstream when you have cancer.

If you already have had prostate cancer treatment, changes in PSA levels can tell whether treatment is working.

After surgical removal of your prostate, your PSA levels should be undetectable. After radiation therapy, the PSA levels should drop and remain at low levels.

Signs that your cancer has returned may include one of these:

  • Three consecutive PSA rises above the lowest level over time
  • Confirmed rise of more than 2 ng/mL from your lowest level

The key is watching your PSA levels over time. A rapid rise suggests rapid cancer growth and the need for treatment. A very slow rise of the PSA can often be watched.

But PSA levels can also be somewhat confusing. For example, they can go up and down a bit for no reason. The PSA test is not precise, and minor changes from test to test are to be expected.

Also, PSA levels tend to be higher in older men or men with large prostates.

Low rises of PSA levels can't predict your longevity or symptoms when you have cancer. But high or rapidly rising PSA levels can suggest future problems.

Researchers know that universal PSA cut-off levels don't fully reveal how prostate cancer grows. Everyone is different.

That's why doctors take other factors into account when evaluating your situation. Talk with your doctor to get a better idea of what to expect, so the numbers don't add to your anxiety.

Advanced Prostate Cancer and PSA Levels Over Time

If you have advanced prostate cancer that has spread outside the prostate, your doctor will be looking less at your actual PSA levels than at whether and how quickly PSA levels change.

Doctors use changes in PSA levels over time (called PSA velocity) to tell how extensive and aggressive your cancer is.

Your doctor won't just look at one PSA reading at a time. He or she will confirm it with multiple tests over many months, especially after any radiation therapy. That's because you can have a temporary bump in PSA levels for about one to two years after radiation treatment.

To determine how aggressive your cancer is and whether further treatment makes sense, your doctor may also consider your:

  • PSA levels before cancer
  • Grade of cancer
  • Overall health and life expectancy

PSA Levels and Treatment for Advanced Prostate Cancer

Your symptoms and how long it takes for your PSA levels to double (PSA doubling time) affect decisions about how soon to try treatment such as hormone therapy.

Your doctor will look at how quickly or slowly PSA rises before deciding on which treatment to suggest. You may need continued monitoring before moving to a new treatment. Your doctor may suggest waiting for a while to delay the appearance of treatment-related side effects. Discuss with your doctor how to weigh these considerations.

PSA levels may also be useful in checking if your treatment for advanced prostate cancer is working after you have had:

  • Hormone therapy
  • Chemotherapy
  • Vaccine therapy

Treatment should lower PSA levels, keep them from rising, or slow the rise, at least for a while.

Doctors monitor PSA regularly based on the type of treatment you had first. For example, after hormone therapy, PSA should drop to a lower level quickly. It may fall further over time as you continue hormone therapy.

Combined with symptoms and other tests, PSA tests can also show if it's time to try another type of treatment.