Could changes in PSA levels help detect prostate cancer?
A blood test used to detect prostate cancer - called the PSA test - may be more accurate if it is repeated more than once, to track changes over time, a study suggests.
BMJ Group News
What do we know already?
The PSA test measures the amount of a substance called prostate-specific antigen (or PSA) in a man’s blood. PSA is made in the prostate gland, but can leak into the blood for a number of reasons, including if there is a cancer in the prostate.
PSA levels are measured in units called nanograms per millilitre of blood (ng/ml). If a man’s PSA level is above 4.0 ng/ml, this can suggest a cancer may be present, particularly in men aged between 60 and 69, but it cannot tell for certain. It also cannot tell if a cancer is slow-growing and wouldn’t cause problems in a man’s lifetime, or whether it is growing more quickly and might cause health problems. This means that some men who have the PSA test end up having unnecessary tests and treatments. As a result, most British doctors do not advise men to have the test, unless they have other symptoms or things that put them at risk of prostate cancer, such as a close male relative with prostate cancer.
To improve the PSA test’s accuracy, researchers have proposed looking at the results of the test over time. If PSA levels climb more steeply, this might be a clearer indication of prostate cancer in general and more aggressive cancer in particular.
To test this theory, researchers gathered PSA test results on nearly 220,000 men aged 45 and older from a large US health insurer’s records. All the men had at least three PSA tests over 10 years. The researchers looked at the changes in their PSA levels in relation to whether they were diagnosed with prostate cancer.
What does the new study say?
Overall, the researchers found that looking at the rate of change in PSA levels was only slightly better at detecting prostate cancer than a single raised PSA level of 4.0 ng/ml or higher.
When looking at more aggressive cancers, the researchers found that the rate of change in PSA levels was better at detecting these cancers than prostate cancers in general.
How reliable is the research?
This study looked at a very large group of men over 10 years, which makes its findings more reliable. However, the researchers can’t be certain that all the men who had prostate cancer were diagnosed during the study. This could have affected its results.
Around half of the men in the study were white. We know that some ethnic groups are more likely to have prostate cancer than others. For example, black men are three times as likely to get prostate cancer as white men of the same age. But we can’t be sure if the results apply equally to different ethnic groups.
What does this mean for me?
These findings suggest that looking at the rate of change in PSA levels over time may improve the PSA test’s ability to detect more aggressive cancers, but these findings alone are unlikely to change how doctors use the test. If you have previously had multiple PSA tests, you might ask your doctor how your levels have changed and what this might mean for you.