A new Dutch-led study is adding fuel to the fire of debate about whether a common prostate cancer test really saves lives.
The study finds that the PSA test too often picks up on prostate cancers that are so small and slow-growing, they likely would never have been detected during the man's lifetime -- something Canadian scientists say they've known for years.
"We have known for a long time that PSAs clearly lead to the over-detection of prostate cancer," Dr. Neil Fleshner, of Princess Margaret Hospital in Toronto, told CTV News.
Because of this overdiagnosis, too many men suffer needlessly by undergoing further tests or medications that may not help them live longer, says an editorial that accompanies the study in the Journal of the National Cancer Institute.
One in eight Canadian men develops prostate cancer in their lifetime. However, unlike many other cancers, some prostate cancers never affect a man's health. In fact, it's estimated that two of three Canadians diagnosed with the disease have such slow-growing cancer, they will die of something else before their prostate cancer catches up with them.
"There are many men who develop cancer cells in the prostate that will never grow and bother them and cause trouble in their lifetime," Dr. Peter Scardino, of the Memorial Sloan-Kettering Cancer Center in New York, told CTV News.
The researchers in this latest study wanted to find out how much PSA testing leads to overdiagnosis -- the portion of cancers detected by screening that would not have been otherwise diagnosed during the patient's lifetime.
The team, led by Gerrit Draisma of Erasmus MC in Rotterdam, Netherlands, looked at U.S. men aged 50 to 84 years in 1985 to 2000 and used three models to make their calculations. They found that the proportion of patients overdiagnosed ranged between 23 per cent and 42 per cent of PSA-detected cancers.
The PSA test detects levels of a substance called prostate specific antigen. Elevated levels may indicate problems, including cancer.
The value of PSA testing has been questioned for some time because of its high rate of false-positives. A false positive result can lead to unnecessary follow-up testing, such as biopsies, or even to surgery that can sometimes leave patients incontinent or impotent.
For these reasons, the test is not offered to the general population nor is it covered by some provincial health plans.
The Canadian Cancer Society has concluded that for men with symptoms of prostate cancer, PSA testing can be an important tool in diagnosing the disease. But for those who do not have symptoms, PSA screening does not appear to save lives, they say.
In the U.S., the test is used more often. That's in part because the U.S. Preventive Services Task Force hasn't been able to determine whether to recommend routine PSA testing because of a lack of evidence.
Similarly, the American Cancer Society doesn't recommend routine testing for prostate cancer, though it believes doctors should offer the test to their patients yearly starting at age 50. The American Urological Association similarly believes that doctors should offer prostate cancer testing to their patients yearly starting at age 50.
The Canadian Cancer Society says that men over 50 should talk to their doctor about getting tested for prostate cancer.
Meanwhile, researchers are continuing to study new detection methods as well as new ways to use the PSA test, including serial PSA testing.
This involves testing PSA repeatedly over time and comparing results with earlier results to see how fast antigen levels are rising. Some research indicates that if a PSA level increases quickly, it may indicate cancer.
"These cancers, if they are going to harm the patient, as it shown in this study, it may not happen for 20-25 years and possibly never at all," said Fleshber. "But at least if you know you have it you can monitor it."
With a report from CTV's medical specialist Avis Favaro and senior producer Elizabeth St. Philip
