Many men who've been having PSA tests for prostate cancer must have been surprised to hear last August that men age 75 and older should not be screened. That advice made headlines because it came from the influential U.S. Preventive Services Task Force, which concluded that even though screening can detect cases of prostate cancer early, the benefits of treating these cancers in men over 75 "are small to none," while the risks from treatment are substantial.
What might surprise you even more is that the Task Force waffles about screening for men under 75 - not recommending for or against it - because it says there's no clear evidence that the benefits outweigh the risks at any age. Some experts actually hoped that the Task Force would recommend against routine PSA screening for all men, period.
How can a simple early - detection test for cancer not automatically be a great thing? Here are some arguments for and against PSA screening.
[Editor's Note: In late March, after this article appeared in the Wellness Letter, two important studies in the New England Journal of Medicine concluded that screening for prostate cancer has little or no effect in prolonging men's lives, and that the risks posed by unnecessary treatment may outweigh the benefits of early detection. But many questions remain unanswered, and these and others studies are continuing. Meanwhile, the following discussion is more pertinent than ever.]
The prostate, a small gland between the bladder and rectum in men, produces seminal fluid. Cancer of the prostate is the most commonly diagnosed cancer in men (other than skin cancer) and the second leading cause of cancer deaths in men after lung cancer. The unusual thing about prostate cancer is that the great majority of tumors - especially in older men—remain small, develop very slowly or not at all, do not spread, and cause no symptoms. This cancer is fatal in about 12% of diagnosed cases. Far more men die with prostate cancer than from it. It's estimated that 15 to 30% of American men over age 50, and 60 to 70% of men who reach 80, have small, harmless prostate cancers.
Age increases the risk - about 98% of prostate cancers are diagnosed in men over 55 - and so does a family history of the disease; having a brother or father with prostate cancer doubles the risk. For unknown reasons, black men are twice as likely to develop the cancer as whites, and more likely to die from it.
PSA stands for prostate specific antigen, a protein produced by the prostate and released into the blood. PSA levels rise as a result of prostate disorders—such as infection, benign enlargement, or cancer - or sometimes for no apparent reason. The PSA blood test was introduced in the 1980s to monitor men already diagnosed with prostate cancer. But doctors soon began using it to screen healthy men, and the test has come into wide use.
The problem, though, is that nobody has ever been able to show that PSA testing actually saves lives. Do men live longer if they discover their cancer earlier and undergo treatment? There is still no definite proof.
The PSA test merely detects the presence of a protein in the blood, not cancer. Only about one-third of men with high PSAs turn out to have cancer. The only way to tell which men have cancer is with a surgical biopsy. Moreover, it's possible to have a low PSA and still have prostate cancer. Indeed, about one in five men with prostate cancer does not have an elevated PSA.
Other problems: Though there are several ways to improve the accuracy of PSA testing - such as assessing PSA level in relation to prostate size and monitoring changes in levels over time - there is no way to predict with certainty which cancers (detected by biopsies) will be aggressive and which will stay confined to the prostate and cause no problems. An abnormal PSA test can lead to the discomfort and pain of a biopsy, and, if no cancer is found, unnecessary worry. But the biggest concern is that PSA testing often leads to the aggressive treatment of small, slow-growing cancers that would never have become life-threatening—treatment that is sometimes harmful.
And another concern: If you're diagnosed with prostate cancer, there is no one best treatment. Surgery to remove the prostate and radiation are standard; but both treatments may produce such complications as impotence and incontinence. Fortunately, newer techniques are less likely to damage the nerves essential for erections and urinary control.
For older men "watchful waiting" - now often called "active surveillance" - rather than treatment is often best. This means frequent retesting and monitoring, with an eye to beginning therapy if the localized cancer progresses. Studies comparing watchful waiting to surgery or radiation therapy have yielded conflicting results.
Despite the unknowns and drawbacks, millions of men are being tested, often because many doctors include the test in routine blood work. The good news is that death rates from prostate cancer have been gradually declining since the 1990s, and its incidence has leveled off. Some researchers attribute this improvement to PSA testing, though this is still debated. Improved treatments also deserve credit.
Last year a study in the urology journal BJU International found a big decline in prostate cancer deaths in the Austrian state of Tyrol, where PSA screening was offered free to men beginning in 1993. Almost 90% of men age 45 to 75 were screened, and by 2005 the death rate from prostate cancer dropped by 54%, compared to a 29% drop in the rest of Austria, where free screening was not available. Another recent study showed that mortality rates from prostate cancer have fallen four times more in the U.S. than in Britain, where far fewer men get PSA tests and the cancer is usually treated less aggressively.
But these were only observational studies, not clinical trials. Several major clinical trials, which should more clearly determine whether or not PSA screening saves lives, are in progress. Results are expected in a few years.
The troubling fact is that for some men a delay in the diagnosis of prostate cancer will be fatal. Every man should discuss the PSA test with his doctor. When the pros and cons are fully described to men who have not yet made up their minds about the test, they are more likely to decide against it, according to a 2007 review article in the American Journal of Preventive Medicine.
Here is what we recommend for PSA screening: