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Prostate-Specific Antigen (PSA) Test Information
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  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 Elevated PSA Advanced Test 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.

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  2. Why is the PSA test performed?

    As with many other routine blood tests, PSA is measured from a small sample of blood. Once a blood sample is taken, the level of PSA in the sample is measured by an accurate laboratory method called an immunoassay. The results are usually reported in ng/ml, shorthand for nanograms per milliliter.  The U.S. Food and Drug Administration (FDA) has approved the PSA test for use in conjunction with a digital rectal exam (DRE) 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 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 (recurred). 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 Elevated PSA Advanced Test 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 patientís body. Patients 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.

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  3. 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 National Cancer Institute (NCI) 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 oneís chance of dying from prostate cancer.

    Doctorsí 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 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 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.

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  4. How are PSA results reported?

    PSA test results report the level of PSA detected in the blood. There are several different ways to measure PSA. Most physicians think that the "normal range" is between 0 and 4.0 nanograms per milliliter (ng/ml) for the most common PSA tests. (Because some PSA tests have different normal ranges, you should check with your physician on this point.) 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 lab's "normal" upper level is simply a cutoff point used to separate men who are less likely to have prostate cancer from those for whom further prostate cancer testing may be appropriate, depending upon the circumstances.  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 indicated.


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  5. What causes PSA to rise?
    The level of PSA in the bloodstream may be elevated by an process that leads to an increase in the number of cells making PSA or to a breakdown of the normal barriers in the prostate that prevent much PSA from getting into the bloodstream. The most common condition leading to a high PSA is benign (noncancerous) enlargement of the prostate, called benign prostatic hyperplasia (BPH). BPH is very common in men over the age of 50 and may lead to difficulty with urination. Infection or inflammation in the prostate, called prostatitis, may also cause elevation of PSA by damaging the PSA barrier in the prostate. In addition, some diagnostic tests, such as a needle biopsy of the prostate, may increase PSA levels for several weeks. It does not appear that a routine digital rectal examination (DRE) of the prostate by the doctor's finger causes an elevation of the PSA.

    Both BPH and prostate cancer are common in men over the age of 50. In addition, there is a lot of overlap in blood PSA levels between men with BPH and those with early prostate cancer. These factors limit the usefulness of PSA as a tool for detecting curable prostate cancer. Many patients who have a PSA level higher than 4 ng/ml will eventually be found not to have prostate cancer. These men have a "false-positive" test. If PSA is tested on men with BPH but no prostate cancer, as many as one-third to one-half of such men will have an elevated PSA. Their PSA results, however, are generally in the 4 to 10 ng/ml range.

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  6. 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 manís 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.

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  7. 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 manís chance of dying from prostate cancer. PSA testing may identify very slow-growing tumors that are unlikely to threaten a manís 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.
    In addition to false-positive tests, the PSA may be falsely negative -- that is, normal even when prostate cancer is present. Some 30 to 40 percent of patients with early-stage prostate cancer have a normal PSA. Repeating PSA tests once every year may be useful to find some of the cancers in men who have a normal PSA at first.

    False-negative and false-positive findings limit the value of PSA testing. Despite this, PSA testing has led to an increase in the detection of prostate cancer.

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  8. Why is the PSA test controversial?
    Using the PSA test to screen men for prostate cancer is controversial because it is not yet known if the process 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.

    The procedures used to diagnose prostate cancer may cause significant side effects, including bleeding and infection. Prostate cancer treatment often causes incontinence and impotence. 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.

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  9. What research is being done to improve the PSA test?
    Scientists 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:
    • PSA velocity: PSA velocity is based on changes in PSA levels over time. A sharp rise in the PSA level raises the suspicion of cancer.
    • Age-adjusted PSA: Age is an important factor in increasing PSA levels. For this reason, some doctors use age-adjusted PSA levels to determine when diagnostic tests are needed. When age-adjusted PSA levels are used, a different PSA level is defined as normal for each 10-year age group. Doctors who use this method suggest that men younger than age 50 should have a PSA level below 2.5 ng/ml, while a PSA level up to 6.5 ng/ml would be considered normal for men in their 70s. Doctors do not agree about the accuracy and usefulness of age-adjusted PSA levels.
    • PSA density: PSA density considers the relationship of the PSA level to the size and weight of the prostate. In other words, an elevated PSA might not arouse suspicion in a man with a very enlarged prostate. The use of PSA density to interpret PSA results is controversial because cancer might be overlooked in a man with an enlarged prostate.
    • Free versus attached PSA: PSA circulates in the blood in two forms: free or attached to a protein molecule. With benign prostate conditions, there is more free PSA, while cancer produces more of the attached form. Researchers are exploring different ways to measure PSA and to compare these measurements to determine if cancer is present. In clinical practice, free PSA serves as an additional tool to help decide which men need more aggressive evaluation to check for prostate cancer, including a prostate biopsy, and which men might be safely managed with observation including serial exams and PSA tests over time. In men presenting with a high standard total PSA test (certainly any value over 10) or with a suspicious digital rectal examination of the prostate, there is no recognized utility for obtaining an additional free PSA test. In most such cases, prostate biopsy is indicated to rule out cancer. Free PSA has been proposed as a secondary test in men with a slight elevation or abnormality of the standard total PSA level, who otherwise have no suspicion of prostate cancer on their physical exam, and who perhaps have an enlarged prostate (BPH) which might also cause a mild elevation of the PSA levels above normal. If the percent free PSA compared to total PSA is high in such an individual, several preliminary clinical studies have suggested that it might be safe to avoid a biopsy of the prostate. This might be particularly beneficial in patients in whom prostate biopsy is technically difficult, such as those who are on medical anticoagulation (blood thinners) for a variety of cardiovascular problems, or the man whose rectum has been surgically removed because of rectal cancer. It should be emphasized throughout this discussion that the proper use of free PSA is still a matter of scientific study and debate. Any man with an abnormally elevated standard PSA test but a "normal" percent free PSA who chooses, after careful consideration with his or her physician, to avoid a prostate biopsy, should have careful medical observation, including repeat PSA tests and prostate exams done on a regular basis.
    • Other screening tests: Scientists are also developing screening tests for other biological markers, which are not yet commercially available. These markers may be present in higher levels in the blood of men with prostate cancer.
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