The Prostate-Specific Antigen (PSA) Test: Questions and Answers

Overview
  • Prostate-specific antigen is a protein produced by the cells of the prostate gland. The PSA test measures the level of PSA in the blood.
  • The U.S. Food and Drug Administration has approved the use of the PSA test along with a digital rectal exam to help detect prostate cancer in men age 50 and older. The FDA has also approved the PSA test to monitor patients with a history of prostate cancer to see if the cancer has come back.
  • Doctorsí recommendations for screening vary.
  • The higher a manís PSA level, the more likely it is that cancer is present, but there are many other possible reasons for an elevated PSA level.
  • The PSA screening test has limitations and is still controversial.

  1. What is the prostate-specific antigen test?
  2. Prostate-specific antigen is a protein produced by the cells of the prostate gland. The PSA test measures the level of PSA in the blood. The doctor takes a blood sample, and the amount of PSA is measured in a laboratory. Because PSA is produced by the body and can be used to detect disease, it is sometimes called a biological marker or tumor marker.

    It is normal for men to have low levels of PSA in their blood; however, prostate cancer or benign conditions can increase PSA levels. As men age, both benign prostate conditions and prostate cancer become more frequent. The most common benign prostate conditions are prostatitis and benign prostatic hyperplasia. 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.

    PSA levels alone do not give doctors enough information to distinguish between benign prostate conditions and cancer. However, the doctor will take the result of the PSA test into account when deciding whether to check further for signs of prostate cancer.

  3. Why is the PSA test performed?
  4. The U.S. Food and Drug Administration has approved the PSA test along with a digital rectal exam to help detect prostate cancer in men age 50 and older. During a DRE, a doctor inserts a gloved finger into the rectum and feels the prostate gland through the rectal wall to check for bumps or abnormal areas. Doctors often use the PSA test and DRE as prostate cancer screening tests; together, these tests can help doctors detect prostate cancer in men who have no symptoms of the disease.

    The FDA has also approved the PSA test to monitor patients with a history of prostate cancer to see if the cancer has come back. An elevated PSA level in a patient with a history of prostate cancer does not always mean the cancer has come back. A man should discuss an elevated PSA level with his doctor. The doctor may recommend repeating the PSA test or performing other tests to check for evidence of recurrence.

    It is important to note that a man who is receiving hormone therapy for prostate cancer may have a low PSA reading during, or immediately after, treatment. The low level may not be a true measure of PSA activity in the manís body. Men receiving hormone therapy should talk with their doctor, who may advise them to wait a few months after hormone treatment before having a PSA test.

  5. For whom might a PSA screening test be recommended?
  6. Doctorsí recommendations for screening vary. Some encourage yearly screening for men over age 50, and some advise men who are at a higher risk for prostate cancer to begin screening at age 40 or 45. Others caution against routine screening, while still others counsel men about the risks and benefits on an individual basis and encourage men to make personal decisions about screening. Currently, Medicare provides coverage for an annual PSA test for all men age 50 and older.

    Several risk factors increase a manís 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 nearly 70 percent of prostate cancer cases occurring in men age 65 and older. Other risk factors for prostate cancer include family history, race, and possibly diet. 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 Asian and Native American men have the lowest rates. In addition, there is some evidence that a diet higher in fat, especially animal fat, may increase the risk of prostate cancer.

  7. How are PSA test results reported?
  8. PSA test results report the level of PSA detected in the blood. The test results are usually reported as nanograms of PSA per milliliter of blood. In the past, most doctors considered PSA values below 4.0 ng/ml as normal. However, recent research found prostate cancer in men with PSA levels below 4.0 ng/ml. Many doctors are now using the following ranges, with some variation:

    There is no specific normal or abnormal PSA level. However, the higher a manís 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 needed.

  9. What if the test results show an elevated PSA level?
  10. 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 no other symptoms suggest cancer, the doctor may recommend repeating DRE and PSA tests regularly to watch for any changes. If a manís PSA levels have been increasing or if a suspicious lump is detected during the DRE, the doctor may recommend other 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, x-rays, or cystoscopy. Medicine or surgery may be recommended if the problem is BPH or an infection.

    If cancer is suspected, a biopsy is needed to determine if cancer is present in the prostate. During a biopsy, samples of prostate tissue are removed, usually with a needle, and viewed under a microscope. The doctor may use ultrasound to view the prostate during the biopsy, but ultrasound cannot be used alone to tell if cancer is present.

  11. What are some of the limitations of the PSA test?
  12. Why is the PSA test controversial?
  13. Using the PSA test to screen men for prostate cancer is controversial because it is not yet known if this test actually saves lives. Moreover, it is not clear if the benefits of PSA screening outweigh the risks of follow-up diagnostic tests and cancer treatments. For example, the PSA test may detect small cancers that would never become life threatening. This situation, called overdiagnosis, puts men at risk for complications from unnecessary treatment such as surgery or radiation.

    The procedure used to diagnose prostate cancer may cause side effects, including bleeding and infection. Prostate cancer treatment may cause incontinence and erectile dysfunction. For these reasons, it is important that the benefits and risks of diagnostic procedures and treatment be taken into account when considering whether to undertake prostate cancer screening.

  14. What research is being done to validate and improve the PSA test?
  15. The benefits of screening for prostate cancer are still being studied. The National Cancer Institute is currently conducting the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, or PLCO trial, to determine if certain screening tests reduce the number of deaths from these cancers. The DRE and PSA are being studied to determine whether yearly screening to detect prostate cancer will decrease a manís chance of dying from prostate cancer. Full results from this study are expected in several years. Scientists also are researching ways to distinguish between cancerous and benign conditions, and between slow-growing cancers and fast-growing, potentially lethal cancers. Some of the methods being studied are:

    For additional information about prostate cancer, contact the NCIís Cancer Information Service.

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