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What Does Prostate Specific Antigen Do

What Research Has Been Done To Study Prostate Cancer Screening

Prostate-specific antigen test ‘does more harm than good’

Several randomized clinical trials of prostate cancer screening have been carried out. One of the largest is the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, which NCI conducted to determine whether certain screening tests can help reduce the numbers of deaths from several common cancers. In the prostate portion of the trial, the PSA test and DRE were evaluated for their ability to decrease a mans chances of dying from prostate cancer.

The PLCO investigators found that men who underwent annual prostate cancer screening had a higher incidence of prostate cancer than men in the control group but the same rate of deaths from the disease . Overall, the results suggest that many men were treated for prostate cancers that would not have been detected in their lifetime without screening. Consequently, these men were exposed unnecessarily to the potential harms of treatment.

A second large trial, the European Randomized Study of Screening for Prostate Cancer , compared prostate cancer deaths in men randomly assigned to PSA-based screening or no screening. As in the PLCO, men in ERSPC who were screened for prostate cancer had a higher incidence of the disease than control men. In contrast to the PLCO, however, men who were screened had a lower rate of death from prostate cancer .

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What Is A Prostate

A prostate-specific antigen test measures the level of PSA in your blood. The prostate is a small gland that is part of a man’s reproductive system. It is located below the bladder and makes a fluid that is part of semen. PSA is a substance made by the prostate. Men normally have low PSA levels in their blood. A high PSA level may be a sign of prostate cancer, the most common non-skin cancer affecting American men. But high PSA levels can also mean noncancerous prostate conditions, such as infection or benign prostatic hyperplasia, a noncancerous enlargement of the prostate.

Other names: total PSA, free PSA

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What Is Considered An Elevated Prostate

Researchers havent settled on a single normal PSA level. Previously, a level of 4.0 ng/mL or higher would lead to more testing, usually a prostate biopsy. During the biopsy, a healthcare provider removes a small sample of prostate tissue to check it for cancer.

However, healthcare providers now consider other issues together with the PSA level to decide whether to perform a biopsy. Your age, general health, family history and health history factor into the decision.

Prostate Specific Antigen And What You Need To Know

Prostate Specific Antigen (PSA) Test: Results, Accuracy ...

Here are the things you need to know about Prostate Specific Antigen test and the risk level at specific age

What is a PSA Test and How is Being Done?

The Prostate Specific Antigen test measures the amount of PSA in the bloodstream. There is PSA present in the blood of all men who have a prostate gland, but the level is usually quite low. Healthy men with no cancer or other issues with their prostate have a low amount of PSA present in their blood stream.

However, when the prostate grows larger, the amount will increase and when it reaches a certain level will be considered high enough to cause further examination.

Prostate glands will grow larger for a few reasons which include the presence of cancer which includes injury, a rectal exam that was performed digitally, or sexual activity that includes ejaculation. If there has not been any sexual activity, digital rectal exam, or injury to the prostate, then further examination becomes warranted.

In addition, there are medical conditions which will cause the prostate to grow as well, including prostatitis and benign prostatic hyperplasia or BPH. So, a biopsy of the prostate will then be performed to detect the presence of cancer cells.

So, an increase in the levels of prostate specific antigen is not actually cancer detection, but instead an increase in the size of the prostate with cancer being a possibility. Still, a PSA blood test is considered one of the standard means of detecting cancer in the prostate.

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Screening For Early Disease

The purpose of any screening test is to detect disease before it becomes clinically evident. Routine measurements of blood pressure and cholesterol are examples of screening tests that have proved their worth. In the realm of cancer screening, Pap tests for cancer of the cervix, mammograms for breast cancer, and various tests for colon cancer have gained widespread acceptance.

A screening test is successful if it meets several goals:

  • It has a high sensitivity that is, it detects a high percentage of cases while missing few

  • It has a high specificity that is, it doesnt falsely diagnose disease when none is present

  • The test is reliable and reproducible and also safe, convenient, and inexpensive enough to gain widespread acceptance

  • Above all, the test must lead to a treatment that will improve the patients quality of life, extend the duration of his life, or both. In a word, the test should do more good than harm.

  • The Case Against Psa Screening

    The Canadian Task Force on Preventive Health Care and the Canadian Urological Association recommend against PSA testing in men who seem healthy. The U.S. Preventive Services Task Force recommends against testing for men age 75 or older as well as for men with life expectancies of 10 years or less. For other men, the task force notes that the “potential harms of screening for prostate cancer can be established, the presence or magnitude of potential benefits cannot.” The American College of Physicians and American Academy of Family Physicians agree that men should be counseled about “the known risks and uncertain benefits of screening for prostate cancer” before they undergo any testing.

    They, too, have a point. Even at an average cost of $40, the annual testing of all American men over 50 would cost billions of dollars. Still, it might save money if early diagnosis could reduce the need for even more expensive treatment of advanced cancer. But critics go beyond economics to consider the problem of overdiagnosis. The PSAgnostics have long argued that screening might produce more harm than good if it leads to unnecessary treatment in men who would never be harmed by their prostate cancers.

    For all their differences, the PSAdvocates and PSAgnostics have agreed on one point: the only way to resolve the issue is with high-quality randomized clinical trials. And that’s just why the two studies are so important.

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    How Much Does The Test Cost

    The price of a PSA test will vary based on where the test is conducted and whether you have health insurance. If you have health care coverage, you can reach out to your insurance provider directly to find out what a PSA test will cost under your plan. Depending on your plan, you may be responsible for out-of-pocket costs, such as copays and deductibles.

    The cost of at-home PSA testing ranges from about $30 to $70.

    What Are The Risks Of A Psa Test

    Prostate-specific Antigen (PSA) Tests for Prostate Cancer

    Drawing blood is considered safe. However, because veins and arteries vary in size and depth, getting a blood sample isnt always simple.

    The healthcare provider who draws your blood may have to try several veins in multiple locations on your body before they find one that allows them to get enough blood.

    Drawing blood also has several other risks. These include risk of:

    • fainting

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    The Test Is Often Not Needed

    Most men with high PSAs dont have prostate cancer. Their high PSAs might be due to:

    • An enlarged prostate gland.
    • Recent sexual activity.
    • A recent, long bike ride.

    Up to 25% of men with high PSAs may have prostate cancer, depending on age and PSA level. But most of these cancers do not cause problems. It is common for older men to have some cancer cells in their prostate glands. These cancers are usually slow to grow. They are not likely to spread beyond the prostate. They usually dont cause symptoms, or death.

    Studies show that routine PSA tests of 1,000 men ages 55 to 69 prevent one prostate cancer death. But the PSA also has risks.

    Noncancerous Causes Of A High Psa

    The PSA test was originally approved by the U.S. Food and Drug Administration in 1986 to monitor the progression of prostate cancer in men diagnosed with the disease. By 1994, it was clear that the test also had value in detecting prostatic inflammation in otherwise symptom-free men.

    While prostate cancer is clearly the main focus of concern, other noncancerous conditions can also cause the PSA to rise. The most common of these is prostatitis . It is, in fact, the most common cause of prostate problems in men under 50 and can take several forms:

    • Acute bacterial prostatitis, most often caused when bacteria leaks from the urinary tract into the prostate gland
    • Chronic bacterial prostatitis, characterized by persistent inflammation
    • Chronic non-specific prostatitis, for which there may be symptoms but no known cause
    • Chronic asymptomatic prostatitis, for which inflammation is present but with no symptoms

    Another cause for elevated PSA levels is benign prostatic hyperplasia , a condition by which the gland itself becomes enlarged. BPH is primarily seen in older men and may cause uncomfortable urinary symptoms, including the impairment of the urinary flow. While it isn’t entirely clear what causes BPH, many believe it to be related to changes in sex hormones as men get older.

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    Does Your Psa Indicate Cancer

    Prostate Specific Antigen or PSA, is an enzyme found in a man’s blood produced exclusively by prostate cells. An abnormal rise in PSA, can indicate Prostate Cancer. Higher levels of PSA can be found in the blood as prostate cancer cells begin to proliferate in an uncontrolled way.

    Normal PSA levels in the blood are very small amounts between 0-2.5 ng/ml. As a man ages his prostate can become larger, leading to slightly higher normal levels of PSA. It is important to have your PSA and prostate exam as part of your yearly physical.

    Testing for PSA, requires that a man’s blood be drawn and sent to the lab for analysis. If higher than normal levels are discovered, action is recommended. Levels greater than 2.5 ng/ml, can have many different causes. Prostate Cancer is one cause. But elevated PSA levels doesn’t necessarily mean prostate cancer. PSA can also rise for benign, non-cancerous conditions such as enlarged prostate, prostate inflammation, infection, or trauma. Get checked by your doctor.

    IMPORTANT: All elevated readings of PSA should be checked.

    Prostate Specific Antigen or PSA, is an enzyme found in a man’s blood produced exclusively by prostate cells. An abnormal rise in PSA, can indicate Prostate Cancer. Higher levels of PSA can be found in the blood as prostate cancer cells begin to proliferate in an uncontrolled way.

    IMPORTANT: All elevated readings of PSA should be checked.

    The Case For Psa Screening

    Interpreting PSA values in Prostate Cancer

    The American Cancer Society recommends that doctors discuss annual PSA testing with every man above the age of 50 who has a life expectancy of 10 years or longer it also calls for yearly discussions to start at the age of 45 for men at increased risk, including African Americans and men with family histories of prostate cancer. The ACS says that if a man cannot decide, his doctor should recommend testing. The American Urological Association also recommends PSA screening. Until 2009, they had the same guidelines as the ACS, but their guidelines now call for doctors to offer the test to all men with a life expectancy of at least 10 years, beginning at age 40.

    They have a point. Requiring only a single blood sample, PSA testing is quick, easy, and safe. With a typical cost of about $40, it is inexpensive, and technical improvements have made it reliable in most labs.

    Advocates of PSA screening point out that the test has the potential to detect about 80% of prostate cancers. Without screening, some 40% of prostate cancers are not diagnosed until they have spread too far to be curable. Early detection is surely the best hope for curing prostate cancer, and PSA screening is the best way to find early disease.

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    Does An Elevated Psa Level Always Mean Cancer

    Though there is always some risk of the test resulting in a “false negative” , an increase in PSA levels may be caused by:

    • A prostate gland biopsy
    • A resection of the prostate
    • Rigorous physical activity related to the prostate
    • Excessive doses of chemotherapeutic drugs
    • Prostatitis
    • Enlarged prostate
    • The test returns an elevated PSA level that, after further testing, reveals there is no underlying condition

    Production In Benign Hyperplasia

    The majority of PSA is produced by the glands in the transitional zone of the prostate. This portion of the prostate is associated with benign prostatic hyperplasia . The peripheral zone, where 80% of prostate cancers originate, produces very little PSA.

    The Hybritech monoclonal assay produced a measurement of 0.5 ± 0.4 ng/mL. Using the monoclonal assay, Lee et al calculated a serum PSA elevation of 0.12 ng/mL per gram of benign prostatic tissue.

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    Screening Tests For Prostate Cancer

    Screening is testing to find cancer in people before they have symptoms. Its not clear, however, if the benefits of prostate cancer screening outweigh the risks for most men. Still, after discussing the pros and cons of screening with their doctors, some men might reasonably choose to be screened.

    The screening tests discussed here are used to look for possible signs of prostate cancer. But these tests cant tell for sure if you have cancer. If the result of one of these tests is abnormal, you will probably need a prostate biopsy to know for sure if you have cancer.

    Psa Transition Zone Density

    The Prostate Specific Antigen (PSA) Test

    Kalish introduced PSA density of the transition zone as a refinement to the original PSAD. This refinement is predicated on the following 2 assumptions:

    • That measuring transition zone volume with TRUS is more accurate than measuring the entire prostate volume because of the difficulty in measuring the true border of the apex in the longitudinal view

    • That most of the PSA entering the circulation arises from the transition zone

    Zisman et al have offered a new index using the peripheral zone fraction of PSA to predict the presence of prostate cancer in men with PSA levels of 4-10 ng/mL. They point out that the PZ contributes little to tPSA. The PZ fraction can be calculated by using the following formula:

    tPSA Ã /total prostate volume

    PZ volume is measured by subtracting TZ volume from total prostate volume while neglecting the central zone.

    Zisman et al compared the positive and negative predictive values using tPSA, PSAD, PSA-TZ, and PSA peripheral zone density . The efficacy rates of PSA and PSA-TZ were similar, at 60% PSA-PZ had a 70% efficacy rate, PSAD an 80% rate. The negative predictive values were superior to the positive predictive values, ranging from 78% to 83% for PSA, from 78% to 88% for PSAD, from 87% to 92% for PSA-TZ, and from 81% to 100% for PSA-PZ.

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    What Is The Accuracy Of The Psa Test

    One of the limitations of the PSA test is that PSA is not specific to prostate cancer and that it can be affected by several common conditions such as benign enlargement of the prostate, inflammation, and infection of the prostate. Furthermore, there is some variability in PSA results when using different testing equipment. One study showed that 25% men who had an initial PSA result between 4 ng/mL and 10 ng/mL had a normal test result when it was repeated.

    Limitations of PSA testing include a high false-positive rate . In fact, only about 25% of men who have an elevated PSA between 4 ng/mL and 10 ng/mL will have prostate cancer identified on prostate biopsy and 75% will not. If one uses a lower cutoff of 3.1 ng/mL, PSA had a sensitivity of 32% and specificity of 87% for identifying prostate cancer.

    Another concern in addition to the low specificity in detecting the presence of prostate cancer is the inability of the test to discriminate between a more aggressive, high-risk, prostate cancer from one that is less likely to cause harm, or a low-risk prostate cancer. This is thought to lead to overtreatment in up to 50% of men with prostate cancer.

    How Do I Prepare For A Psa Test

    If your doctor requests that you have a PSA test, make sure that theyre aware of any prescription or over-the counter medicines, vitamins, or supplements you take. Certain drugs may cause the test results to be falsely low.

    If your doctor thinks your medication might interfere with the results, they may decide to request a different test or they may ask you to avoid taking your medicine for several days so your results will be more accurate.

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    Psa In Other Biologic Fluids And Tissues

    Concentration of PSA in human body fluids

    female serum 0.01 – 0.53

    It is now clear that the term prostate-specific antigen is a misnomer: it is an antigen but is not specific to the prostate. Although present in large amounts in prostatic tissue and semen, it has been detected in other body fluids and tissues.

    In women, PSA is found in female ejaculate at concentrations roughly equal to that found in male semen. Other than semen and female ejaculate, the greatest concentrations of PSA in biological fluids are detected in breast milk and amniotic fluid. Low concentrations of PSA have been identified in the urethral glands, endometrium, normal breast tissue and salivary gland tissue. PSA also is found in the serum of women with breast, lung, or uterine cancer and in some patients with renal cancer.

    Tissue samples can be stained for the presence of PSA in order to determine the origin of malignant cells that have metastasized.


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