ORLANDO, Fla. (AP) _ A common blood-scanning test for prostate cancer, an annual medical ritual for millions of older men, can safely be done less frequently for the majority who have low readings, a major study concludes.
The federally funded study concludes the risk is so low for these men that checking once every two years, or even every five years, is enough to find cancer in time.
About half of all men over age 50 now get a regular PSA test, which scans the blood for a protein that goes up as prostate cancer develops.
Researchers said that if their new guidelines are followed, the less-frequent testing would cut the number of PSA tests each year in half, saving between $500 million and $1 billion.
Dr. E. David Crawford of the University of Colorado, who directed the analysis, presented the results Monday at a meeting in Orlando of the American Society of Clinical Oncology.
``When we first thought about screening, we thought it should be done every year,'' he said. ``We had no data to suggest otherwise. Now we have data that lets us step back.''
Doctors generally recommend further testing if men's PSA levels rise above 4 nanograms per milliliter of blood. The new study concludes:
_ If a man's initial PSA reading is between zero and 1, he can wait five years before having another test.
_ If the reading is between 1 and 2, he can wait two years before another test.
_ Those whose readings are between 2 and 4 should continue to have annual tests.
If followed, the study results will mean less testing for the majority of men. The study was conducted on 27,863 men between ages 55 and 74, and 55 percent had initial PSA readings under 2.
The study was designed primarily to ask a bigger question: Does early detection of prostate cancer save lives? The answer is not known yet. So far, there are no results from any research to prove that finding the cancer sooner does any good, although many doctors believe early detection saves lives.
``These findings sit amid a much larger controversy about whether PSA screening should be done at all,'' said Dr. Steven Woolf of Virginia Commonwealth University.
Falsely positive test results cause anxiety and lead to unnecessary biopsies. Furthermore, many men live with slow-growing prostate cancers that never cause any problems. Finding and removing them can cause incontinence and impotence without giving any benefit.
``It's important to understand there are potential benefits to screening, but people also need to understand more about the harms of screening,'' Woolf said.
The latest study found that when men's PSA readings are between zero and 1, 98.7 percent will still have a reading under 4 when tested again five years later. For those with readings between 1 and 2, 98.8 percent will still be under 4 when tested two years later.
Whether a cutoff of 4 will remain as the point of concern is not clear. Some doctors already suggest that more testing should be done if men's PSA levels go above 2.6.
The American Cancer Society now recommends that annual PSA testing and a digital rectal exam be offered to men beginning at age 50 if they have a life expectancy of at least 10 years.
Dr. Harmon Eyre, the cancer society's research director, said the latest study findings look reasonable.
``I won't say that we will immediately change our guidelines, but we will take a careful look at it,'' he said.
Besides the absolute PSA number, doctors also take into consideration how fast the level is rising, the size of the man's prostate and his age when deciding how aggressively to react to their readings.
For instance, men with enlarged prostates often have higher PSA readings, although this does not necessarily mean they have cancer.
When readings are between 4 and 10, experts say there is about a 40 percent chance the man has prostate cancer. Over 20, the risk is virtually 100 percent.
Prostate cancer is second to lung cancer as a cancer killer of men, resulting in 30,000 deaths annually.