More than one million American men have gone through needless treatment for prostate cancer since the PSA test became common more than 20 years ago, a medical journal study says.
And the study’s author says Canadian men face the same problem of “overdiagnosis,” causing them to have surgery and radiation treatment that can cause impotence, incontinence and pain.
This doesn’t mean diagnosing cancer where none exists, says the study and editorial in Monday’s Journal of the National Cancer Institute. It means that many men had a form of cancer that could have been left alone safely.
Doctors have long known this can happen with PSA tests, which measure a chemical in the body whose level increases when prostate cancer is present, the study says. But the authors claims to have the first firm count of how many men are affected.
The PSA test (it stands for prostate-specific antigen) is designed as a way to detect cancer in an early stage. But lead author Dr. Gilbert Welch of the U.S Department of Veterans Affairs says having such a test shouldn’t cause more cancers to be detected.
It should, he says, allow doctors to find the same number of cancers – but find them earlier. That’s not what has happened. Since 1986, Welch estimates, American doctors have detected 1.3 million more prostate cancer cases than they would have found without the PSA test. Of those men, just over a million had cancer treatment.
“This is definitely a problem in Canada, as well,” he said, though he does not use Canadian statistics in his study.
“Most of this excess incidence (number of cases) must represent overdiagnosis,” his study concludes.
“I don’t think it’s widely understood yet,” said Welch, an internal medicine specialist.
“Many people don’t understand the human cost of being overdiagnosed – being told you have cancer” even though “that cancer will never cause symptoms or death in your lifetime. We don’t know which patients are overdiagnosed, so we treat them all.”
Men in their fifties are now 3.6 times more likely to be diagnosed with prostate cancer than before the PSA test. Men younger than 50 are now 7.2 times more likely to be diagnosed, according to the study.
“We appear to be taking what used to be a disease of older men and turning it into a disease of young men,” he said.
In an editorial in the same journal, the chief medical officer of the American Cancer Society argues that while the death rate from prostate cancer is dropping (down 40 per cent since 1993), “the reasons are not known” and the PSA test may not be responsible. Dr. Otis Brawley says an American survey shows no benefit of screening, while a European study shows the PSA test does save lives. But even the European study shows “substantial overdiagnosis,” he says. “More than 1,400 men have to be screened and 48 additional men diagnosed and treated to avert one prostate cancer death.”
He adds: “Prostate cancer screening has resulted in substantial overdiagnosis and unnecessary treatment. It may have saved relatively few lives . . .
“We desperately need the ability to predict which patient has a localized cancer that is going to metastasize and cause suffering and death and which patient has a cancer that is destined to stay in the patient’s prostate for the remainder of his life.”
In Canada, “we have been seeing similar trends in the increase of the rates of cancers being diagnosed,” said Heather Chappell, acting director of cancer control policy at the Canadian Cancer Society. “It’s our inability to tell the dangerous cancers from the cancers that you would have lived with all your life and not even known about.”
Research continues into trying to learn the difference, she said.
Meanwhile, “we firmly believe that it (screening) should be a personal choice” for patients. In Canada, about 23,500 men are diagnosed with prostate cancer each year, and 4,400 die from it.