PSA Tests and Prostate Cancer

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"PSA" is a test for a protein called "prostate specific antigen." This protein is produced by the prostate gland and can be measured in the blood. Because PSA levels may be higher in men with prostate cancer, PSA testing has been recommended by some physicians as a method of detecting early prostate cancers in men without symptoms of cancer.

Prostate cancer is extremely common, occurring in about one in eleven older men, and it is the second leading cause of cancer death in men, next to lung cancer. Unfortunately, there is no guarantee that PSA testing performed as part of a routine screening examination will accurately diagnose prostate cancer. The PSA test can miss prostate cancer up to 30 percent of the time; in other words, up to 30% of men with prostate cancer will have a normal PSA level. Just as importantly, the PSA can be abnormally elevated or "positive" in men with no prostate cancer. Of all men with an abnormal PSA, only 25-30% will prove to have prostate cancer; the other 70-75% will undergo further testing, which is often invasive, only to be found to have a normal prostate gland.

Furthermore, even when it accurately detects the presence of a cancer, the PSA test cannot distinguish between prostate cancers which are likely to spread and endanger your health, vs. "innocent" prostate cancers which grow very slowly. "Innocent" or silent prostate cancers can be present for many years without spreading to other areas of the body, and this type of cancer does not affect your health or shorten your life. Studies indicate that a majority of prostate cancers are "innocent," and suggest that many prostate cancers found in PSA screening programs are innocent ones.

Not all prostate cancers are innocent. Over 40,000 men die of prostate cancer in the U.S. each year. Aggressive, rapidly growing prostate cancers can spread to lymph nodes, bones, and other areas of the body. The theoretical reason for PSA testing is to find these aggressive cancers and treat them before they can spread.

If you choose to have a PSA test and the result is abnormal, further tests will be needed to establish the presence or absence of prostate cancer. The PSA test may simply be repeated; if it is mildly elevated at a stable level over a period of months or years, it is less likely to represent cancer. Or, an ultrasound test may be needed; this test uses sound waves to generate pictures of the prostate gland, and may show areas which have an appearance different from the normal prostate gland texture, indicating possible cancer. The definitive test to determine the presence of cancer is a biopsy, in which a needle is inserted through the rectum into the prostate gland to obtain a sample of prostate tissue for analysis. But even the results of a biopsy may not accurately predict whether an individual person's cancer will be aggressive or slow-growing.

1. Do nothing except for "watchful waiting." For slower growing cancers, which are unlikely to spread or cause ill health, this may be the best option. In some situations, this may even be the best choice for persons with more aggressive cancers, since the other treatment options (surgery and radiation treatment) may not improve the chances of surviving and may only decrease your quality of life.

2. Radiation treatment of the prostate gland. Potential complications include: a risk of death (in 0.2 to 0.5% of persons), a risk of impotence (about 40%), a risk of incontinence or loss of bladder control (1 to 3%), a risk of narrowing (scar formation) in the urethra (the channel which carries urine to the tip of the penis), and a risk of rectal injury (2 to 23%) which may be serious enough to require a colostomy (1%).

3. Surgical removal of the prostate gland. Complications include: a risk of death from surgery (0.3 to 2%), a risk of impotence (20 to 85%), a risk of incontinence (1-27%), a risk of narrowing of the urethra (up to 20%), and a risk of rectal injury (1 to 3%) which may require a colostomy (1%).

4. Hormonal therapy. Various hormonal treatments are available; however, these are considered "palliative" rather than "curative" - that is, they are generally used to control symptoms such as pain from cancer which has spread to other areas of the body, and do not improve life expectancy or permanently stop cancer growth.

Although it is hoped that early detection of prostate cancer through PSA screening will be effective in improving the chances of survival for men with prostate cancer, this effect has not yet been demonstrated in long-term studies. Because of this, together with the potential harm which can occur with attempts at treatment of prostate cancer, PSA screening is not recommended by the National Cancer Institute or the U.S. Preventative Services Task Force. On the other hand, PSA screening is endorsed by the American Cancer Society for men between the ages of 50 and 70; please note that even the American Cancer Society does not advocate PSA screening for men under the age of 50 or over the age of 70.

Thus, it cannot be said that there is a "right" or "wrong" way to proceed with regard to PSA screening. It is a personal decision, deserving discussion with your physician. If you are interested in further reading about prostate cancer, you may wish to visit the Health Library at Stanford (located at the Stanford Shopping Center, co-sponsored by the Palo Alto Medical Foundation), or consult the following article:

"Screening for Prostate Cancer with Prostate-Specific Antigen: An Examination of the Evidence," by S. H. Woolf; New England Journal of Medicine, Nov. 23, 1995, vol. 333, no. 21, p. 1401.

...from the Physicians at the Los Altos Center
Palo Alto Medical Foundation
370 Distel Circle
Los Altos, CA. 94022
(650-254-5200)