December 1, 2010
Prostate cancer: To screen or not to screen
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At first glance, this request seems prudent. Prostate cancer is diagnosed in one in six men at some point in their lifetime, and it is the second leading cause of cancer death (after lung cancer). Prostate-specific antigen (PSA) blood tests and digital rectal exams can result in early detection. If cancer is found, surgery, radiation therapy and even watchful waiting are treatment options.
What complicates the matter is that early detection may lead to unnecessary treatments, especially since most prostate cancers progress slowly. For this reason, new guidelines released by the American Cancer Society in March encourage doctors to involve patients more fully in the decision to get screened before any tests are offered.
The best time to begin this discussion is determined by the patients age and other risk factors:
• At 50, for men at average risk with at least a 10-year life expectancy.
• At 45, for men at higher risk because they are African-American or have a first-degree relative (father or brother) diagnosed with prostate cancer before 65.
• At 40, for men at appreciably higher risk because multiple family members have been diagnosed with prostate cancer before 65.
Results published in 2009 from two randomized and controlled trials of prostate cancer screening played a major role in developing these guidelines. One study, a 17-year trial by the National Cancer Institute, found no evidence that screening reduced prostate cancer deaths at follow-up intervals of seven and 10 years.
A second study of European men indicated that screening reduced the rate of prostate cancer death by 20 percent. But for every life saved, 1,400 men need to be screened and 48 treated. Because of the large number of men exposed to treatment risks without improved outcomes, this trial also contributed to concerns about the value of screening.
To make an informed choice, men should start by considering the limits of screening and what they will do if their test results are positive. Neither the digital rectum exam nor the PSA test is completely reliable. For example, elevated PSA levels can be caused not only by prostate cancer but also by conditions such as an enlarged prostate (benign prostatic hyperplasia or BPH) and prostatitis, an inflammation or infection of the prostate. In contrast, even normal PSA levels do not guarantee that men are cancer free.
With screening, men may experience anxiety if the tests are positive. They also must decide if they will have a biopsy. While a biopsy can confirm the presence of cancer, it too has limits as a diagnostic tool. It can result in false negatives (if cancer cells are missed), and it does not indicate the aggressiveness of most detected cancers.
If prostate cancer is found, the next decision is whether the benefits of treatment outweigh the risks. With slow-growing prostate cancers, men often will die from some other cause. In fact, the relative survival rate of men diagnosed with prostate cancer is 100 percent after five years, 91 percent after 10 years, and 76 percent after 15 years.
Treatment choices include surgery to remove the prostate (radical prostatectomy) and radiation therapy to kill the cancer cells. Both of these approaches may lead to serious and unpleasant side effects, such as impotence and incontinence, without necessarily resulting in a longer life.
Faced with these choices, some men will choose screening while others will wait. Even though the final decision is up to each patient, this discussion with a health-care professional is an important part of mens health. By learning about the disease, they can make informed choices now. Like their doctors, they can also watch for medical advances that will improve screening tools and treatments for prostate cancer in the future.
Edward Dy, M.D., is a board certified internal medicine doctor at the UW Medicine Neighborhood Clinic in Kent/Des Moines and a UW clinical assistant professor.