Prostate-specific Antigen (PSA) Test

About the Prostate-specific Antigen (PSA) Test

This tumor marker is used for screening for prostate cancer, and should be accompanied by a rectal exam for a cancer diagnosis. The PSA test also helps monitor patients who have already undergone prostate cancer treatment.

What Your PSA Levels Mean

A high level of PSA can be affected by different factors: noncancerous growths of the prostate may show a higher level of PSA; older men or men with larger prostates may also show elevated levels of PSA but may not be diagnosed with cancer.

Cancer is usually unlikely with a blood PSA level below 4 ng/mL. Levels between 4 ng/mL and 10 ng/mL may be considered abnormal, and a level greater than 10 ng/mL means there is a high likelihood for a cancer diagnosis. Patients who show a level greater than 4 ng/mL usually require a prostate biopsy to study the tissue for cancer.

When PSA levels are between 4 and 10 ng/mL doctors may study the ratio between two types of PSA: those bound to proteins and those which are free. A higher amount of free PSA means a lower chance of prostate cancer. Free PSA of more than 25% of the total PSA means prostate cancer is unlikely. Free PSA below 10% means the chance of prostate cancer is about 50% higher.

Tracking PSA Levels with Your Doctor

The effectiveness of a treatment cannot always be measured by a single PSA test. Higher PSA levels aren’t always a sign of cancer. Changes in levels may be due to normal changes in your body, variations in lab testing or your age. Work with your healthcare team to understand what tests are being used to evaluate your progress.