With the exception of skin cancer , prostate cancer is the most common cancer diagnosed in men. Doctors routinely use the prostate-specific antigen (PSA) blood test to screen men over the age of 50. This test is used because the presence of prostate cancer often causes PSA levels to increase in the blood. An abnormal PSA test often leads to more invasive testing and possibly even surgery.

However, the PSA test is unable to distinguish between prostate cancer and other, less serious conditions—such as benign prostatic hyperplasia —and most men who have an abnormal test do not have cancer. For this and other reasons, many health professionals question whether PSA testing is an effective means of prostate cancer screening.

A study published in the May 28, 2003 Journal of the American Medical Association supported previous findings that there are natural variations in PSA levels over time. The researchers found that PSA levels frequently fluctuated into and out of the normal range. In fact, about half the men whose PSA levels were abnormal at the beginning of study found their levels dropping down into the normal range sometime during the study.

About the Study

Researchers from the Memorial Sloan-Kettering Cancer Center and the National Cancer Institute used data from the Polyp Prevention Trial, a study that evaluated the effect of a low-fat, high-fiber diet on the recurrence of colon polyps. For this study, the researchers performed PSA tests on the stored blood samples of the 972 men who had no history of prostate cancer. At the start of the study, the men were healthy, with a median age of 62.

The men had blood samples taken annually for four years. A PSA test was performed on the five available blood samples for each participant. Test results were classified according to the following criteria:

  • A PSA level above 4 nanograms per milliliter (ng/mL) – commonly used cutoff point for abnormal levels in clinical practice
  • A PSA level above 2.5 ng/mL – a more sensitive cutoff point
  • An age adjusted cutoff point, which accounts for normal prostate enlargement with age
  • Percentage of free PSA below 25 or a PSA velocity above 0.75 ng/mL per year – both of which may better distinguish prostate cancer from other PSA-elevating conditions

The Findings

Over the four-year period, between 15 and 30% of the men had at least one abnormal PSA level—depending on the cutoff criteria used. Of the men whose PSA level was above 4 ng/mL, 30% had a normal PSA level one year later and 44% returned to normal sometime before the study ended. Most of the men whose PSA levels returned to normal maintained normal levels one year later. These findings may be limited by the fact that some of men might have actually had undiagnosed prostate cancer at the start of the study.

How Does This Affect You?

This study suggests that men who have a single abnormal PSA test should wait at least six weeks and then have a follow-up PSA test before undergoing further invasive testing or surgery. If you have an abnormal PSA test result, talk to your doctor about repeating the test before taking more aggressive steps. And remember, three out of every four men who have persistently abnormal PSA levels test negative for prostate cancer after a biopsy .

While having an even mildly elevated PSA level can be anxiety provoking, there is really no rush. Since most prostate cancers progress very slowly, in the unlikely event that you are ultimately diagnosed with prostate cancer, the tumor is unlikely to grow and spread while you are waiting to have a follow-up PSA test. It is far better to be sure about the result before undergoing any invasive procedure.