A blood test that screens men for prostate cancer has sparked much controversy: Some doctors argue that it does more harm than good, while cancer survivors say screening – any type of screening – saves lives.
But a new study aims to silence the debate, and lend new credence, to the PSA test.
Researchers in the United States have found that a screening method that uses the power of drug therapy and changes in PSA levels over time is more likely to detect aggressive prostate cancer. The study, published Thursday in the Journal of Urology, confirms earlier observations and has the potential to evolve into the standard of care when diagnosing prostate cancer.
Steven Kaplan, the study’s lead investigator, said the use of specific medications helps eliminate the “background noise” so that the focus can be on improving prostate cancer diagnosis.
The PSA test is an indicator of inflammation, which can be due to other things besides cancer. For instance, many older men suffer from benign prostatic hyperplasia (BPH), or a swollen prostate, which can made it difficult to urinate. This condition can also push up PSA levels.
And even if a patient has cancer, a PSA test can’t determine the severity of cancer, and doctors (and patients) may unnecessarily opt for surgery or other forms of intervention.
“Nobody ever said it was a PCSA test – a prostate cancer specific antigen. It’s not; it’s a prostate specific antigen. It measures a lot of things in the prostate, like enlargement, inflammation. And if we could make it work a little bit better, then it will also be a better marker for cancer,” said Dr. Kaplan, director of the Iris Cantor Men’s Health Centre at New York-Presbyterian/Weill Cornell and a professor of urology at Weill Cornell Medical College.
Dr. Kaplan and his team used the screening method to understand the cancer risk in men who have abnormal PSA readings despite negative biopsies. They used two drugs – finasteride and dutasteride – that are designed to treat BPH and reduce an enlarged prostate.
The study did not involve a large group – 276 men whose PSA levels were greater than four and who had two or more negative biopsies. But even with a small sample size, what the researchers discovered could deepen our understanding of detecting prostate cancer.
In one phase of the study, almost 100 patients were given the two drugs daily and their PSA measured at six months and then a year. A biopsy was also performed after a year. The drug therapy reduced PSA in all the men, but the reduction was significantly greater in men with benign prostate disease and significantly less in patients whose prostate biopsy detected cancer.
In the second phase of the study, 179 patients had the same drug therapy. But only those with a certain change in their PSA reading – almost 30 per cent of patients – had a biopsy. Of those men, more than half had cancer.
The researchers found the drug therapy to be effective in eliminating variables, such as inflammation, that lead to a high PSA result. The authors concluded that if PSA readings remained persistently high despite the medication and even though the prostate had shrunk or if PSA levels rose after falling, it could indicate the presence of cancer.
“Is it a perfect marker? No. But do these medications make it a better marker? Absolutely,” Dr. Kaplan said. “We want to eliminate the benign reasons why PSA can go up. These drugs help to do that. And by doing that, we can make the changes in PSA more reflective of cancer and not benign diseases.”
Prostate cancer is deadly. The disease will kill an estimated 4,000 men in Canada this year.
Most patients group and urologists recommend routine PSA screening. But recently, a blue-ribbon U.S. government panel advised men to forgo the routine screening, saying widespread testing saves few lives and leads to a lot of unnecessary treatment with significant side effects, such as incontinence and impotence.
Laurence Klotz, professor of surgery at the University of Toronto, said the problem is not the test itself, but how some doctors opt to aggressively treat patients with positive PSA results. He said that Dr. Kaplan’s screening method is useful. He cautions that it is a small study that requires validation in a larger sample of patients.
“It is quite promising and many clinicians are already using the drugs this way,” Dr. Klotz said.