Prostate-specific antigen (PSA)
Prostate-specific antigen (PSA) is present in low concentrations in the blood of all adult males. It is produced by both normal and abnormal prostate cells. Elevated PSA levels may be found in the blood of men with benign prostate conditions, such as prostatitis (inflammation of the prostate) and benign prostatic hyperplasia (BPH), or with a malignant (cancerous) growth in the prostate. While PSA does not allow doctors to distinguish between benign prostate conditions (which are very common in older men) and cancer, an elevated PSA level may indicate that other tests are necessary to determine whether cancer is present.
PSA levels have been shown to be useful in monitoring the effectiveness of prostate cancer treatment, and in checking for recurrence after treatment has ended. In checking for recurrence, a single test may show a mildly elevated PSA level, which may not be a significant change. Doctors generally look for trends, such as steadily increasing PSA levels in multiple tests over time, rather than focusing on a single elevated result.
Researchers are studying the value of PSA in screening men for prostate cancer (checking for the disease in men who have no symptoms). At this time, it is not known whether using PSA to screen for prostate cancer actually saves lives. The National Cancer Institute-supported Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial is designed to show whether the use of certain screening tests can reduce the number of deaths caused by those cancers. For prostate cancer, this trial is looking at the usefulness of regular screening using digital rectal exams and PSA level checks in men ages 55 to 74.
Researchers are also working on new ways to increase the accuracy of PSA tests. Improving the accuracy of PSA tests could help doctors distinguish BPH from prostate cancer, and thereby avoid unnecessary follow up procedures, including biopsies.
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