What are some of the limitations of the PSA test?

* Detecting tumors does not always mean saving lives: When used in screening, the PSA test can detect small tumors. However, finding a small tumor does not necessarily reduce a man's chances 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 that have potential risks and significant financial costs and can create anxiety for the patient and his family. Most men with an elevated PSA test result turn out not to have cancer; only 25 to 35 percent of men who have a biopsy due to an elevated PSA level actually have prostate cancer (3).

* 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.

PSA Velocity's Clinical Usefulness Remains Unclear

ScienceDaily (Oct. 10, 2007) — Some studies have suggested that the rate of change of prostate-specific antigen (PSA) levels may correspond with prostate cancer survival. But this does not necessarily mean that PSA velocity will be valuable as a prostate cancer screening tool, according to a commentary published online October 9 in the Journal of the National Cancer Institute.

PSA velocity has been the subject of much research and debate since the beginning of the PSA screening era. Initially, PSA velocity was proposed for use in men with moderately elevated PSA levels in order to decrease the number of unnecessary biopsies. But often PSA velocity is being used in men with low PSA levels, effectively increasing the number of men who are referred to have a biopsy.

Ruth Etzioni, Ph.D., of the Fred Hutchison Cancer Research Center in Seattle and colleagues reviewed several recent articles on PSA velocity. They point out in their commentary the important differences between studies of PSA velocity in the cancer screening setting and studies of PSA velocity and prostate cancer progression after diagnosis. These differences lead them to question whether PSA velocity is useful for early detection of prostate cancer.

No studies to date have addressed the costs and benefits of using PSA velocity for prostate cancer screening. "One of the main goals of this commentary has been to reconcile some of the inconsistencies across studies by highlighting features of study design and potential sources of bias that might explain why different types of studies have produced differing results," the authors write.

Prostate-Specific Antigen Blood Test (PSA Test)

What Is It?

The prostate-specific antigen blood test (PSA test) is a screening test that measures the amount of a chemical called prostate-specific antigen (PSA) in a man's blood. PSA is a chemical made by the prostate, a sex gland located near a man's bladder that makes the fluid in semen. PSA levels normally increase as a man ages, but a higher-than-normal PSA level can mean that cancer has developed in the prostate gland. However, high levels of PSA also can be found in other conditions that are noncancerous, including prostatitis (inflammation of the prostate) and benign prostatic hyperplasia, an enlargement of the prostate that affects many older men.

What It's Used For

PSA is used mainly as a screening test for cancer of the prostate. In men who have been diagnosed with prostate cancer, PSA is measured to determine if the cancer has returned after surgery or whether the cancer is growing or shrinking after treatment with hormones or radiation.

The question of whether to do screening tests for prostate cancer remains controversial. Prostate cancer is the most commonly diagnosed cancer in men in the United States and the second leading cause of cancer death in this group. PSA testing can be used to detect the earliest stage of prostate cancer, before the disease causes any symptoms. Many experts believe that PSA testing is the best way to reduce a man's chance of dying of prostate cancer. This is because the early stages of prostate cancer are much more likely to be curable.

However, other experts fear that if PSA is overused, some men will be diagnosed and treated for cancers that have little potential to cause harm. Many older men develop prostate cancer that never spreads and never causes any problems. Most of these harmless cancers would go undetected if screening was not done. Since treatment for prostate cancer can have serious side effects, screening all men for prostate cancer might end up causing more harm than good. Unfortunately, there is no reliable way to determine in advance which cancers need treatment and which are likely to be harmless.

Studies are being done that will help to settle this controversy. In the meantime, most expert panels that make recommendations about cancer screening do not recommend routine PSA testing for all older men. Instead, they encourage men who are at risk of the disease to make an individual decision about screening, after they have discussed the risks and benefits with their health care professionals.

A man who decides to undergo screening for prostate cancer might think the following:

"The PSA test is the best way to protect myself from prostate cancer. Even if it saves one life, it is worth the uncertainty and all of the possible side effects of treatment. I'm one of those people who just likes to know."

A man who chooses not to be screened might think this way:

"No one is sure if screening really helps, and it may actually lead to unnecessary treatment. I think I'll wait until we know more."

For men who want to be screened for prostate cancer, the PSA test usually is combined with a digital rectal exam. Most experts recommend that screening be done every one to two years, beginning at age 50. Men with an increased risk of prostate cancer may wish to begin screening at age 45. This includes African-American men, who have a 70 percent higher rate of prostate cancer than white men, and men whose father or brother has been diagnosed with prostate cancer.

PSA testing is likely to be less useful in men older than age 75 and men who have serious medical problems or other reasons for a limited life expectancy. This is because it may take a decade or more for prostate cancer to grow from the stage at which it can be first detected to the point where it causes symptoms or harm.

Preparation

Ejaculation can cause your PSA to rise briefly, so you should avoid sexual activity for at least 48 hours before having your PSA level tested. Since blood for your PSA test probably will be taken from your arm, wear a shirt or sweater with sleeves that roll up easily. If you recently have had cystoscopy or needle biopsy of the prostate, let your doctor know so you can schedule your PSA test at another time. Those exams can raise PSA levels for a few weeks, which may make it harder to interpret the result of your PSA test. PSA testing also should not be done until several weeks after you have been treated for a urinary tract infection.

How It's Done

Blood for a PSA test usually is drawn from a vein in the crook of your elbow. The area from which blood will be taken will be cleaned with an alcohol swab, and a sterile needle will be used to draw a few ounces of blood into a tube. The puncture site will be covered with a small gauze or bandage. Your blood sample will be sent to a lab where the PSA level is measured.

Follow-Up

Call your doctor for your PSA test results about one week after your blood has been drawn. If your result is abnormal, your doctor may recommend further blood tests or additional testing, such as a prostate ultrasound or a biopsy of the prostate.

Risks

Having your blood drawn is a simple procedure and there are few, if any, risks. However, when used as a screening test, PSA does have some risks, including:

* A risk that your PSA test will be abnormal and that you will need to undergo further testing, such as a prostate biopsy. Keep in mind that as many as three-quarters of men with an elevated PSA level do not have prostate cancer. However, many men who are told that their PSA test is abnormal will have some anxiety until final results are available.

* A risk that screening will lead to treatment for prostate cancer that may or may not be necessary, but that may cause serious side effects.

* A risk that your PSA level will be normal even if you do have prostate cancer.

Be sure to discuss these risks and the benefits of PSA testing with your doctor before you have your blood drawn.

When To Call A Professional

Call your doctor if blood continues to ooze from the needle puncture site or if the site becomes red, swollen or painful.

Prostate Cancer Gene Test Provides New Early Detection

ScienceDaily (Oct. 17, 2008) — Prostate cancer (PCa) is one of the most common male cancers in the Western world. Currently, early detection of PCa depends on an abnormal digital rectal examination and an elevated prostate-specific-antigen (PSA) level requiring a prostate biopsy, often associated with anxiety, discomfort, complications, and heavy expenses.

The prostate-cancer-gene-3 (PCA3) test is a new PCa gene-based marker carried out with a urine sample. PCA3 is highly specific to PCa and has shown promising early detection results at repeat biopsy. It may allow patients to avoid unnecessary biopsies. The PCA3 gene is dominant in over 95% of malignant prostate tissue compared to benign and normal prostate tissue.

Several studies have been done to evaluate the PCA3 assay. In 2007, Marks et al showed that urine PCA3 levels were more accurate than serum PSA measurements for predicting the results of repeat biopsy (Marks LS, Fradet Y, Deras IL, et al. PCA3 molecular urine assay for prostate cancer in men undergoing repeat biopsy. Urology 2007; 69:532–5).

In the October 2008 issue of European Urology, Haese et al took the study by Marks et al even further in their evaluation of the PCA3 assay in a larger population of European men with one or two negative biopsies scheduled for repeat biopsy in order to determine its effectiveness in detecting PCa at repeat biopsy.

The PCA3 score was calculated and compared to biopsy outcome. The diagnostic accuracy of the PCA3 assay was compared to the percentage of free prostate-specific antigen (%fPSA). Most of the PSA that circulates in the serum is attached to larger protein substances, so called 'complexed' PSA. The rest of the PSA is unbound or 'free'. Research suggests that PSA created by prostate cancer is more likely to be the 'complexed' type while non-cancerous or benign PSA is more the 'free' type.

In 463 men, the positive repeat biopsy rate was 28%. The probability of a positive repeat biopsy increases with rising PCA3 scores. The PCA3 score was superior to %fPSA for predicting repeat prostate biopsy outcome and may be indicative of clinical stage and significance of PCa.

The utility of the PCA3 score is independent of the number of previous biopsies, prostate volume, and total PSA.

PSA - what is it?

PSA or Prostate Specific Antigen is a protein which is secreted into ejaculate fluid by the healthy prostate. One of its functions is to aid sperm movement. Normally, only very low levels of the enzyme are able to enter the blood stream. However, because in cancer the normal structure of the tissue is disrupted, considerably more PSA is able to leak into the blood stream, and for this reason, a raised level of PSA in blood (or serum) can indicate the presence of prostate cancer.