Should You Get a PSA Test?
Walter Petersen gets a digital rectal exam and a prostate-specific antigen (PSA) test for prostate cancer as part of his yearly physical. For 10 years, he scored a 2 on the PSA test, which is normal. But in the spring of 1998, his PSA level shot up to 4.2. Three months later, it was 6.2. Time for a biopsy, his doctor told him. The biopsy showed he had prostate cancer. Today, after undergoing radioactive seed implant treatment, Mr. Petersen is cancer-free.
"My digital rectal exam was normal and I had no symptoms," says Petersen. "If it wasn't for the PSA test, no one would have known I had cancer."
Stories like Petersen's make it hard to understand why doctors disagree about how useful the ]]>prostate-specific antigen test]]> really is. Some doctors believe it detects prostate cancer early enough to reduce deaths and prolong life expectancies. Others say there's no proof it does either. Even authoritative bodies like the US Preventive Services Task Force and the American Cancer Society don’t see eye-to-eye on the PSA test.
What Is the PSA Test?
The PSA test is a simple blood test that measures the levels of prostate-specific antigen in your blood. It's usually done during a routine physical. All prostates—healthy and unhealthy—produce PSA, so it's normal to have some PSA in your blood. And it's normal for that level to rise as you get older. But PSA levels that rise too high or too fast may indicate prostate cancer.
Readings of 0-4 are considered normal unless the level is rising rapidly, as was the case with Mr. Petersen. Some scientists believe that a level above 2.0 ng/ml is of concern in men with a family history of prostate cancer, or in men younger than 60 years of age. Others believe a PSA level above 1.0 ng/ml in men younger than 40 years of age is also of some concern. As men age, so does the secretion of prostate antigen, and therefore a level of 4-5 in men over 70 years old is generally acceptable. Much higher than a value of 7 is reason for concern, and many scientists will perform other tests to clarify an elevated PSA test (PSA velocity or density, or percentage of free PSA).
What Do the Results Mean?
A high blood PSA level may mean you have prostate cancer. Then again, you may not. Therein lies one problem with the test. It's great at measuring high levels of PSA in your blood, but not as good at telling you why it's high. You may have a prostate infection ( ]]>prostatitis]]> ) or benign enlargement of the prostate ( ]]>benign prostatic hyperplasia, or BPH]]> ). Levels also go up temporarily after sex, or after having a digital rectal exam.
Only 15-20% of men with high PSA levels have prostate cancer. The cancer rate is higher (40% or even greater) among men with PSAs greater than 10, but that means a lot of men with high PSA levels don't have cancer. In other words, the test produces a lot of what doctors call "false-positives," results that falsely indicate prostate cancer. "Some men have PSAs of 30," says, David Arvold, MD, an internist at St. Mary's/Duluth Clinic in Duluth, Minnesota, "but they don't have cancer."
The test also produces many "false-negatives," meaning some men with normal PSA levels may have prostate cancer. Most prostate cancers are slow-growing and may exist for decades before they are large enough to cause symptoms. Subsequent PSA tests may indicate a problem before the disease progresses significantly.
Say you have a PSA test and your levels are high. What should you do next?
You could repeat the test at an appropriate interval to see if the value is rising. Doctors call this "watchful waiting," and under the right conditions it can be the best choice for many men (like Walter Petersen who waited three months for his repeat test). But, especially if you are younger, you'll proceed to the next level and get a biopsy of your prostate. If the biopsy is negative, that's good news, but a biopsy can miss the cancer because the samples analyzed came from a noncancerous part of your prostate. So a second biopsy may be called for. A second negative biopsy may be good news or it may indicate that it is difficult to find the cancerous cells within your prostate that are causing the elevated PSA test. But what if the biopsy's positive?
If the cancer is aggressive, it should be treated, unless you're quite old. If it's not aggressive, your quality of life may be better if the cancer is left untreated. It's impossible for doctors to predict which cancers will blossom into life-threatening problems and which won't. Most do not. They just continue to grow slowly without any significant ill effects.
The Problems With Treatment
Some studies support Dr. Arvold's opinion that many men—perhaps even most men—would do better not to treat early prostate cancer because the side effects of treatment can be worse than the disease. Fifty percent of men who have their prostates removed become permanently impotent, according to research published in the Annals of Internal Medicine , and 20-30% have some permanent loss of bladder control.
Even external beam radiation treatment poses a significant risk of impotence and a 10% chance for permanent bowel problems, though new techniques may reduce these risks significantly.
"If you treat with ]]>external beam radiation]]> or surgically remove the prostate," says Dr. Arvold, "your likelihood for a diminished quality of life is high." Radioactive seed implants pose the lowest risk for complications, but less than half of the men with prostate cancer are eligible for this procedure, and although early results look promising, the jury is still out on how effectively this procedure prolongs your life.
Fewer Men Dying
Nationwide, 60% of all prostate cancers are now discovered before they spread outside the gland.
"The test allows us to detect a cancer on average five years earlier," says Michael Blute, MD, a urologist at the Mayo Clinic in Rochester, Minnesota. "That translates into a better chance the cancer can be effectively treated."
The Mayo Clinic strongly believes in the PSA test and has the research to support that opinion, according to Dr. Blute. Their research shows that among men in their 50s and 60s living in Olmstead County, Minnesota, "incidence of late-stage prostate cancer has decreased since the mid-1990s when the PSA test caught on," says Dr. Blute. "We've also seen an overall decrease in the incidence of prostate cancer. And now, most importantly, we've seen a reduction in death rates."
James Talcott, MD, director of the Center for Outcomes Research at the Massachusetts General Hospital Cancer Center, is not so sure the decline in death rates is due to the PSA test. "It's possible," he says, "that the improved statistics may be due to other factors like changes in men's diets and how data are collected."
PSA Gaining Popularity
Despite disagreement among the medical community, conventional medical wisdom increasingly favors using the test, even for men who have no symptoms or family history. According to Jeff Engelsgjerd, MD, a urologist at St. Mary's/Duluth Clinic, the PSA test is, for now, the best way to detect early stage prostate cancer, when it is most treatable.
"It's not a perfect test," he says, "but for now, it's the best thing we have." Dr. Engelsgjerd recommends that all his patients over age 50, regardless of risk factors, have a yearly PSA test and digital rectal exam.
In February 2000, the American Urological Association (AUA) convened a panel of doctors who developed a set of PSA test recommendations and policies. The panel agreed that PSA tests are at least partially responsible for the dramatic increase in detecting prostate cancer and finding most prostate cancers before they spread outside the gland. The panel also recommended that PSA tests be used in conjunction with digital rectal exams.
"There is still controversy about whether the PSA test saves lives," says Dr. Blute. "However, the AUA panel of experts believes it will eventually be proven that it does save lives."
As a last thought, one must recall the reason for performing a screening test in the first place. A screening test must be reliable and must allow a doctor to identify a disease that can be treated effectively. In treating the disease, the doctor or scientist must prove that detecting the disease at an earlier stage will result in a better outcome than if the disease was identified at a later, more advanced stage. There is no question that early stage prostate cancer is very unlikely to kill a patient, while more advanced stage disease is far more likely to prematurely shorten a man’s life.
Proponents of screening with PSA suggest that the screening test identifies disease at an early and curable point. Opponents suggest that so few men die of prostate cancer, especially older men, that we are probably over-treating many men. Regardless of the debate, using PSA as a screening tool is appropriate because it does what it is supposed to do; it picks up prostate cancer at an early stage. Dealing with the diagnosis of the cancer is the debatable point.
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Last reviewed September 2006 by ]]>Lawrence Frisch, MD, MPH]]>
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