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Prostate Cancer and PSA Screening

If you could find a screening test able to detect a potentially deadly cancer, it would be hailed as a lifesaver and widely recommended, wouldn't it? Not necessarily. The fact that the prostate-specific antigen (PSA) blood test detects prostate cancer in its early stages is undisputed. But whether it should be used as a routine screening tool is one of the most controversial issues in men's health today.

The prostate is a walnut-sized gland located under the bladder and next to the rectum. It provides about a third of the fluid that propels sperm through the urethra and out of the penis during sex. According to the American Cancer Society (ACS), more than 241,000 American men are diagnosed with prostate cancer each year. That makes it the second most common cancer in men after skin cancer. About 28,000 men die of the disease annually, which ranks prostate cancer second only to lung cancer in cancer deaths among American men.

PSA is a protein made by the prostate cells. The PSA test measures the amount of PSA in the blood.

PSA screening has revolutionized the way doctors diagnose prostate cancer over the past two decades. The PSA test can find prostate cancer earlier than the digital rectal exam, the other major test for the disease. Because of the popularity of the PSA test, the number of men diagnosed with prostate cancer has climbed dramatically, but experts disagree about whether this is beneficial.

Here's an overview of the controversy. Prostate cancer usually grows slowly and most often affects older men. This means that detecting it early may not necessarily lead to a longer life. Many men will die years later of other causes, often without ever even realizing they had prostate cancer. That fact can make it difficult to choose treatment, which can have side effects that include impotence, incontinence, or both. The problem is that there is no foolproof way to know if a man will suffer from prostate cancer.

How doctors use the PSA to find prostate cancer

A doctor may consider the level of PSA, how the levels change over time, and your age in deciding whether to recommend a biopsy. A biopsy is the removal of a small amount of prostate tissue. If the biopsy tests positive for cancer, the tissue is evaluated to determine how advanced the cancer is, how likely it is to spread, and which treatment is best. Although these tests provide a great deal of information, none available today can provide a definitive answer on how likely it is that a particular cancer will spread in a particular person.

For use as a screening tool, the PSA test has drawbacks. First, the test is not always accurate. It fails to find prostate cancer in some men who have the disease. Plus, not all prostate cancers cause the PSA to increase. Third, higher than average results usually trigger follow-up testing and biopsies. But many of the results turn out not to be cancer. Most often, the high PSA level is due to noncancerous conditions that are common in older men. These conditions include benign prostatic enlargement and prostatitis, an inflammation of the prostate. Even if cancer is detected, it's often not clear if it requires treatment right away. But knowing they have cancer and not treating it causes anxiety in most men. Because of these varied results, the test doesn't mean a clean bill of health if it's negative and can often cause concern if it's positive.

What experts say about the PSA test

Most scientific and medical organizations such as the U.S. Preventive Services Task Force, the American College of Physicians, the National Cancer Institute, ACS, the American Association of Family Practitioners, and the American College of Preventive Medicine do not recommend routine screening for all men, although the actual recommendations vary.

However, the American Urological Association recommends screening beginning at age 40 for men who are well informed about the risks and benefits of testing and who have at least a 10-year life expectancy. The National Comprehensive Cancer Network recommends that men and their doctors start discussing the pros and cons of screening beginning at age 40. The ACS recommends that men and their doctors discuss the pros and cons of screening before deciding, beginning at age 50 for those at average risk and starting at age 45 for African-American men and those with a strong family history. The U.S. Preventive Services Task Force, on the other hand, now recommends against prostate cancer screening, because the task force believes the benefits do not outweigh the harms. 

Those in favor of regular PSA testing note that the mortality rate for prostate cancer is declining. Those against it say no hard evidence exists to attribute this to PSA screening.

To learn if screening saves lives, the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial was established. The results, published in 2009, found that annual screening with PSA and DRE detected more prostate cancers, but that it did not lower the death rate from prostate cancer. A similar European study found that screening lowered the risk for death slightly, but that about 1,400 men would need to be screened (and 48 treated) in order to prevent one death from prostate cancer.

How to decide if you should get a PSA test

If you're deciding whether to have PSA screening, weigh your feelings about having the test with how you feel about the possible consequences of treatment. Don't overlook the fact that PSA screening is done to find prostate cancer before symptoms develop. If you have any of these symptoms, you should see your doctor:

  • A change in your regular urination pattern

  • Blood in your urine

  • Impotence

  • Pain in your pelvis, spine, hips, or ribs

These symptoms may also be present with noncancerous diseases and should be checked by a doctor.

Also weigh your risk factors to decide whether to have PSA screening. These are the risk factors for prostate cancer:

  • Age. The rate of prostate cancer rises in older men. Bear in mind, though, that this doesn't mean younger men are immune. In fact, the cancer may be more aggressive in younger men.

  • Race. Men of all races must be concerned about prostate cancer, but African-Americans have higher rates. And Asian men have a lower-than-average risk.

  • Family history. Prostate cancer tends to run in families. Fathers, sons, and brothers of patients have twice the risk of men with no affected relatives. Men with three affected relatives face a risk almost 11 times greater than average. Men whose female relatives have a high incidence of breast cancer may have a higher-than-average risk of developing the disease.

How to get the best results if you get a PSA

Most PSA tests measure total PSA, which is the amount that is bound to blood proteins. The free PSA test gives a ratio of PSA found free-floating in the blood to that which is bound with protein. Comparing results from the two tests helps doctors rule out cancer in men whose PSA is mildly elevated due to other causes.

If you have a borderline PSA (between four and 10), you should ask your doctor about this test. Research is also being done on other ways to make the PSA test more accurate and to find other types of blood markers that could be used.

To improve the accuracy of the PSA test, many doctors recommend that men abstain from sex for two days before the test. Also, tell your doctor if you are taking any of these drugs, as they may affect test results:

  • Proscar or Propecia (finasteride)

  • Avodart (dutasteride)

  • Saw palmetto, an herb used by some men to treat benign prostatic enlargement

In the absence of universal agreement on screening guidelines, a man should weigh his personal views and discuss these with his doctor.