A prostate-specific antigen (PSA) test often offers a doctor the first clue about your cancer’s behavior. It’s used as a way to diagnose and monitor prostate cancer. However, the test isn’t a perfect science. There are certain factors this measurement doesn’t account for.

PSA is a type of protein that’s made by both normal cells in your prostate gland and cancer cells. It can be found in your blood and semen. Doctors use a blood test to monitor it. A higher PSA level or one that continues to rise is typically a sign of developing or spreading cancer.

But there has been debate in the medical community about how to properly use the PSA test and how effective it is. Read on to learn what the test can’t tell you.

1. Why your numbers are higher

Factors other than cancer can cause your PSA numbers to rise. The test itself can’t tell doctors exactly what the cause of the higher numbers is.

For example, having a urinary infection, taking certain medications, and getting older are all reasons a PSA could go up. Having a high body mass index can cause a man to have a lower PSA level, but cancer could still be present.

In order to find out if the PSA change is connected to increased cancer growth, your doctor will need to look for patterns in a few of your PSA readings or have you undergo additional screenings.

2. If you need treatment

Not all men who have prostate cancer need treatment, particularly older men (over 70) with very slow-growing cancer. In this case, side effects from treatment might cause more harm and discomfort than living with the cancer.

On the other hand, PSA tests also have the possibility of giving a false negative. This means the levels are low, but cancer is still present. Some prostate cancers that grow quickly don’t produce higher PSA levels, but they do need to be treated.

Measuring PSA alone won’t determine whether treatment is needed or how aggressive the cancer is. Doctors will need to use additional calculations based on the other information gathered from your medical history and/or further screenings.

3. Where cancer has spread

A rise in your PSA can tell doctors there might be increased activity with your prostate cancer, but it can’t pinpoint when or where the cancer has spread. In order to find out what parts of your body have cancer, your doctors will need to perform an imaging test or biopsy.

4. How well your treatment is working

While PSA numbers are a good tool to measure if cancer is growing, not every rise in PSA means a spread in cancer. Sometimes doctors aren’t sure why a person’s PSA goes up.

After certain treatments, like surgery or radiation, it can take some time for PSA numbers to adjust. They may remain higher despite the treatment being effective.

5. When you will have symptoms

PSA numbers don’t predict when a person will experience symptoms from their advanced prostate cancer. In some cases, men with high PSA numbers have been symptom-free, while other men with lower numbers start to physically notice signs from cancer spreading.


One of the main issues with the PSA test is its potential for misdiagnosis. Cancer can be detected and overtreated, causing unnecessary side effects and anxiety.

Sometimes a PSA test can give a false positive. That means the numbers can lead doctors to believe there might be cancer, when in fact there isn’t.

The issue with this situation is that a doctor may recommend a biopsy that isn’t needed. Biopsies can carry a risk of infection, pain, and other complications. For this reason, doctors only recommend them when there is cause for concern.

The takeaway

The PSA test does have its role in prostate cancer diagnosis and monitoring, but it’s a test that still has room for improvement. You’ll likely need to undergo other tests and screenings throughout the course of your treatment to confirm the PSA test findings.

In the future, researchers may get closer to perfecting this test to provide a more accurate reading.