Prostate – Specific Antigen (PSA)

1. What is the prostate-specific antigen (PSA) test?
   PSA is a protein produced by the cells of the prostate gland. The prostate-specific antigen (PSA) test measures the level of PSA in the blood. A blood sample is drawn and the amount of PSA is measured in a laboratory. When the prostate gland enlarges, PSA levels in the blood tend to rise. PSA levels can rise due to cancer or benign (not cancerous) conditions. Because PSA is produced by the body and can be used to detect disease, it is sometimes called a biological marker or tumor marker.
   
   As men age, both benign prostate conditions and prostate cancer become more frequent. The most common benign prostate conditions are prostatitis (inflammation of the prostate) and benign prostatic hyperplasia (BPH) (enlargement of the prostate). There is no evidence that prostatitis or BPH cause cancer, but it is possible for a man to have one or both of these conditions and to develop prostate cancer as well.
   
   Although PSA levels alone do not give doctors enough information to distinguish between benign prostate conditions and cancer, the doctor will take the result of this test into account in deciding whether to check further for signs of prostate cancer.
   
   
2. For whom might a PSA screening test be recommended? How often is testing done?
   The benefits of screening for prostate cancer are still being studied. The DRE and PSA are being studied to determine whether yearly screening to detect prostate cancer will decrease one’s chance of dying from prostate cancer.
   
   Doctors’ recommendations for screening vary. Some encourage yearly screening for men over age 50; others recommend against routine screening; still others counsel men about the risks and benefits on an individual basis and encourage patients to make personal decisions about screening.
   
   Several risk factors increase a man’s chances of developing prostate cancer. These factors may be taken into consideration when a doctor recommends screening. Age is the most common risk factor, with more than 96 percent of prostate cancer cases occurring in men age 55 and older. Other risk factors for prostate cancer include family history and race. Men who have a father or brother with prostate cancer have a greater chance of developing prostate cancer. African American men have the highest rate of prostate cancer, while Native American men have the lowest.
   
   
3. How are PSA test results reported?
   PSA test results report the level of PSA detected in the blood. The PSA level that is considered normal for an average man ranges from 0 to 4 nanograms per milliliter (ng/ml). A PSA level of 4 to 10 ng/ml is considered slightly elevated; levels between 10 and 20 ng/ml are considered moderately elevated; and anything above that is considered highly elevated. The higher a man’s PSA level, the more likely it is that cancer is present. But because various factors can cause PSA levels to fluctuate, one abnormal PSA test does not necessarily indicate a need for other diagnostic tests. When PSA levels continue to rise over time, other tests may be indicated.
   
   
4. What if the test results show an elevated PSA level?
   A man should discuss elevated PSA test results with his doctor. There are many possible reasons for an elevated PSA level, including prostate cancer, benign prostate enlargement, inflammation, infection, age, and race. If there are no other indicators that suggest cancer, the doctor may recommend repeating DRE and PSA tests regularly to monitor any changes.
   
   If a man’s PSA levels have been increasing or if a suspicious lump is detected in the DRE, the doctor may recommend other diagnostic tests to determine if there is cancer or another problem in the prostate. A urine test may be used to detect a urinary tract infection or blood in the urine. The doctor may recommend imaging tests, such as ultrasound (a test in which high-frequency sound waves are used to obtain images of the kidneys and bladder), x-rays, or cystoscopy (a procedure in which a doctor looks into the urethra and bladder through a thin, lighted tube). Medicine or surgery may be recommended if the problem is BPH or an infection.
   
   If cancer is suspected, the only way to tell for sure is to perform a biopsy. For a biopsy, samples of prostate tissue are removed and viewed under a microscope to determine if cancer cells are present. The doctor may use ultrasound to view the prostate during the biopsy, but ultrasound cannot be used alone to tell if cancer is present.
   
   
5. What are some of the limitations of the PSA test?
• Detection does not always mean saving lives: Even though the PSA test can detect small tumors, finding a small tumor does not necessarily reduce a man’s chance of dying from prostate cancer. PSA testing may identify very slow-growing tumors that are unlikely to threaten a man’s life. Also, PSA testing may not help a man with a fast-growing or aggressive cancer that has already spread to other parts of his body before being detected.
• False positive tests: False positive test results (also called false positives) occur when the PSA level is elevated, but no cancer is actually present. False positives may lead to additional medical procedures, with significant financial costs and anxiety for the patient and his family. Most men with an elevated PSA test turn out not to have cancer.
  False positives occur primarily in men age 50 or older. In this age group, 15 of every 100 men will have elevated PSA levels (higher than 4 ng/ml). Of these 15 men, 12 will be false positives and only three will turn out to have cancer.
• False negative tests: False negative test results (also called false negatives) occur when the PSA level is in the normal range even though prostate cancer is actually present. Most prostate cancers are slow-growing and may exist for decades before they are large enough to cause symptoms. Subsequent PSA tests may indicate a problem before the disease progresses significantly.