PSA Results Vary From One Test To The Next

Study Author Recommends Two Tests Before Prostate Biopsy

A new study shows that results from a common blood test used to look for a protein called prostate-specific antigen (PSA) can vary widely from test to test. Men with an abnormally high PSA value on one day may have a normal result on a later retest, authors of the new report say in the Journal of the American Medical Association (JAMA).

A PSA test is used to help detect prostate cancer. PSA is a protein in blood that increases in men with prostate cancer, as well as those with other, benign prostate conditions.

Since PSA levels in blood may vary from day to day, "it's probably prudent to recheck a level" at least six weeks after an earlier test before advising a patient to have a biopsy, says study author Dr. James Eastham, a surgeon at Memorial Sloan-Kettering Cancer Center in New York City.

PSA Testing Value Still Being Debated

Although PSA testing is often encouraged for men over 50, its value as an early-detection tool is not certain, say some experts, and evidence is mixed about whether the exam can prevent deaths from prostate cancer.

"Even with flaws, it is a very useful tool," says Dr. Eastham. "You just have to use it in an appropriate way."

More than 220,000 American men will be diagnosed with prostate cancer this year, and nearly 29,000 will die of the disease, according to the American Cancer Society (ACS). One man in six will be diagnosed with prostate cancer during his lifetime, but only 1 man in 32 will die of this disease.

In addition to an annual physical exam that includes blood, urine, and possibly other lab tests, the ACS suggests consulting your physician about the evaluation of the prostate gland. Tests usually include a digital rectal exam (DRE) and the PSA test.

A DRE and a PSA test are usually conducted annually for men over the age of 50. Men in high-risk groups, such as African-Americans, or those with a strong family history of prostate cancer, may be advised by their physicians to be tested at a younger age.

In the latest research, Dr. Eastham's group followed 972 men enrolled in a seven-year prostate cancer prevention study. The participants, whose average age was 62, had five separate PSA tests drawn over a four-year period.

About one in five men had a PSA level considered high - over 4 nanograms per milliliter of blood - on at least one reading. Yet on a subsequent test, roughly half of these men had fallen back into the normal range for the protein, suggesting the spike was not a signal of prostate cancer.

Second PSA Test Recommended

The ACS says experts at many major scientific and medical organizations, such as the US Preventive Services Task Force, the National Cancer Institute (NCI), and Centers for Disease Control and Prevention (CDC), are discussing PSA testing and its value.

The NCI states that "not all screening tests are helpful, and most have risks such as bleeding or infection due to a biopsy of the prostate for an abnormal PSA blood test. For this reason, scientists at the National Cancer Institute are studying many screening tests to find out how useful they are, and to determine the relative benefits and harms."

"A single abnormal PSA level should be viewed with caution," the researchers write in JAMA. Physicians should confirm the reading "before expensive or invasive tests, such as a prostate biopsy, are recommended," the authors said.

Always consult your physician for more information.

What Are the Symptoms of Prostate Cancer?

There are usually no specific signs or symptoms of early prostate cancer.

The following are the most common symptoms of prostate cancer. However, each individual may experience symptoms differently.

Symptoms may include:

• weak or interrupted flow of urine
• urinating often (especially at night)
• difficulty urinating or holding back urine
• inability to urinate
• pain or burning when urinating
• blood in the urine or semen
• nagging pain in the back, hips, or pelvis
• difficulty having an erection

The symptoms of prostate cancer may resemble other conditions or medical problems.

Always consult your physician for a diagnosis.

 Online Resources

Centers for Disease Control and Prevention (CDC)

Men's Health Network

National Cancer Institute (NCI) Prostate Cancer: Screening and Testing

National Institutes of Health (NIH)

US Preventive Services Task Force

• fat
  Studies suggest that men who eat a high-fat diet may have a greater chance of developing prostate cancer.
  
• fiber
  Dietary fiber intake may influence circulating levels of testosterone and estradiol, which, in turn, may decrease the progression of prostate cancer.
  
• soy protein
  Besides lower fat intake, another major difference between Asian and American diets is the consumption of soy, averaging 35 g/day per capita. Soy contains isoflavone which, in some studies, have been found to inhibit the growth of prostate cancer.
  
• vitamin E and selenium
  Vitamin E, an antioxidant, combined with selenium, has been shown to inhibit tumor growth in lab animals.
  
• carotenoids
  Carotenoids containing lycopenes have been shown to inhibit the growth of human prostate cancer cells in tissue cultures (cells grown in the laboratory). The primary source of lycopenes is processed tomatoes in tomato juice and tomato paste.
  
• herbal preparations
  Combination herbal preparations should be used with caution as reported side effects have included venous thrombosis, breast tenderness, and loss of libido. Many herbal preparations have not been studied in men with prostate cancer.