It's kind of that way when it comes to screening for prostate cancer.
The problem rests with the PSA test. An elevated reading may indicate a tumor, but on the other hand...
"It's only one test, only one view, and you cannot really rely on that alone," said Dr. Israel Barken, a urologist and leader of the San Diego Prostate Cancer Support Group."Some of us say that PSA stands for patient-stimulated anxiety."
It actually stands for "prostate-specific antigen," a substance produced by cells from the prostate gland whose concentration is measured through a blood test.
Combined with the digital rectal exam, or DRE, in which a doctor feels for abnormalities, the PSA is used to screen millions of men annually for prostate cancer.
Yet there is great debate over whether such screening should be done at all.
A study conducted at the VA Connecticut Healthcare System and published last week, for example, found little evidence that PSA and DRE screening reduced deaths.
Dr. John Concato, co-author of the study, said doctors should tell men that screening tests for prostate cancer are flawed and patients should decide for themselves whether to get screened.
Many urologists, however, remain adamant that imperfect screening is better than nothing.
As Barken put it, "Are we overdoing the PSA test? Yes. Should we cut back? No. Why? Because the issue at hand is literally life and death."
The prostate is a walnut-size gland, which only men have, located in front of the rectum and just below the bladder. It creates the fluid that carries sperm.
Prostate tumors, often slow-growing, commonly develop in men age 65 and older.
Yet some prostate tumors are aggressive and spread, becoming life threatening.
Other than skin cancer, prostate cancer is the most common form of cancer afflicting men in the United States, noted Dr. Franklin Gaylis, medical director of the Clinical Outcomes Improvement Program for Sharp Grossmont HealthCare.
An estimated 232,000 American men were diagnosed with prostate cancer in 2005, and 30,000 died from it, Gaylis said. "About 2 million men are battling prostate cancer, and about 3 million more will be diagnosed with it in the next decade."
If found in its early stages, prostate cancer is highly curable.
"It is estimated that more than 17 percent of men will be diagnosed with prostate cancer during their lifetimes. However, there is only a 3 (percent) to 4 percent lifetime risk of dying from prostate cancer," Gaylis said.
Great progress has been made against prostate cancer in the past 15 years, Gaylis said. The number of men discovered to have advanced prostate cancer (usually incurable) has declined to 3 percent from 15 percent, Gaylis said.
But figuring out what PSA results mean is tricky.
Men with what's considered a low PSA reading, generally 2.5 billionths of a gram or lower, have been found to have prostate cancer.
Yet, it is likely that even men with high PSA results, generally four or above, do not have cancer. According to a breakdown by the federal Centers for Disease Control:
If 100 men over age 50 take the PSA test, 85 will have a normal result (though a few will have cancer that was missed); 15 will have a higher than normal result. Of those 15, further tests will show that 12 do not have prostate cancer and three do.
The only way to know for sure is an expensive, invasive and somewhat painful, somewhat risky biopsy, in which tiny samples of prostate tissue are removed with a needle and examined under a microscope.
The PSA test's murky results caused Dr. Thomas Stamey, the Stanford University researcher often credited as the father of the PSA test, to declare in the Journal of Urology recently that the PSA test was useless and should be abandoned altogether.
That stance generated considerable controversy among his colleagues, many of whom view the PSA test as a good tool, if flawed.
"There always was inherent controversy in that we are often screening men whose cancers would never pose a serious risk to their health, men whose cancers are clinically insignificant," said San Diego urologist Dr. Evan Vapnek.
Yet since the PSA test became available in the late 1980s, there has been a definite decrease in prostate-cancer mortality rates.
"Proponents of PSA screening will point to that," Vapnek said.
So should men be screened for prostate cancer or not?
It is not a simple question.
PROS AND CONS
Doctors generally advise men 50 and older to get an annual blood test to check for elevated PSA levels, and a DRE. African-American men (a population with a higher incidence of prostate cancer), and men with a family history of prostate cancer are often advised to begin annual testing at age 45.
"I generally see patients on a longitudinal basis and look for changes in the PSA over time," said Dr. Joseph Schmidt, a urologist, professor and head of the division of urology at the University of California San Diego. "But no matter what, the results still have to be correlated with a DRE and the patient's symptoms."
Symptoms of prostate cancer include blood in the urine; the need to urinate frequently (especially at night); a weak or interrupted flow of urine; pain or burning when urinating; and constant pain in the lower back, pelvis or thighs.
But many men who have prostate cancer exhibit no symptoms, Schmidt noted.
"The best advice for men in this age group - even those in excellent health - is to have this (PSA testing) as part of their regular checkup," Schmidt said.
Given the widespread dissatisfaction with PSA testing, it's not surprising that an enormous amount of research is being done to find a more accurate test. Some recent studies have proven quite promising.
One study, reported in The New England Journal of Medicine in September, holds promise for a test that would be significantly more accurate than the PSA.
Researchers at the University of Michigan and Harvard University took 257 blood samples with PSA levels between 2.5 (low) and 10 (high). The conventional test was almost useless as an indicator since it correctly detected the presence or absence of cancer only half the time, based on biopsy results.
Using the concentration of antibodies (disease-fighting proteins) in the blood to measure the body's immune response to cancer, the Michigan and Harvard researchers were accurate in determining the status of prostate cancer 93 percent of the time.
Other researchers also are making strides toward more reliable tests to detect prostate cancer.
Local urologists cited a promising urine test, uPM3 (offered by Bostwick Laboratories of Richmond, Va.), and research done at the Sidney Kimmel Cancer Center in La Jolla on tests that identify the presence and stage (early, intermediate, advanced) of prostate cancer by examining certain genes in blood or biopsied tissue.
But for now, the PSA test remains the standard.
"As a urologist, I've found it's easier to do the PSA test and then sit down with the patient and say here's what the results mean for you," Vapnek said. "Given what we know right now, that seems a very sensible approach."