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More men with suspicious prostate test results are being monitored for changes in disease progression instead of undergoing immediate treatment, according to a new study in the Canadian Medical Association Journal.

Nearly one-third of patients who underwent monitoring were eventually treated for prostate cancer, the study found.

While the study's senior author and other experts say the results show the prostate-specific antigen test remains relevant and useful, others say it's proof too many men are being overtreated for a disease that would never pose a risk to their health.

Prostate cancer screening is one of the more contentious issues in cancer care today. In 2014, the Canadian Task Force on Preventive Health Care published guidelines recommending against using the prostate-specific antigen test – a blood test that looks for elevated levels of the prostate-specific antigen – to screen for cancer. The task force made the recommendation because evidence shows the PSA test is too unreliable and heightens the risk of overdiagnosis and unnecessary follow-up and treatment.

According to the Canadian Cancer Society, only one in four men with elevated PSA levels has prostate cancer. But when tests show a man has high PSA levels, his doctor may recommend further testing, such as a biopsy, to confirm or rule out the disease. The problem is those follow-up tests can be painful and even lead to serious long-term health problems, such as trouble urinating, erectile dysfunction and infection. Biopsies may also identify and lead to treatment of cancer that is growing so slowly it would never actually pose a risk to the man's health.

But experts such as Dr. Rodney Breau, senior author of the study and surgical oncologist at the Ottawa Hospital, say the PSA test is a valuable tool and that the potential risks can be managed by relying more heavily on active surveillance, which refers to the use of repeat prostate-specific antigen tests, rectal exams and biopsies to look for changes over time.

"Instead of throwing the baby out with the bathwater and just scrapping screening altogether, many people believe if we screen smarter and treat patients more appropriately…then we're going to keep all those benefits of screening and really significantly reduce potential harms that might be associated with it."

In the study, Breau and his colleagues looked back at records of men who had been referred to the Ottawa regional Prostate Cancer Assessment Clinic because of abnormal prostate test results from 2008 to 2013. The researchers focused on 477 patients who were diagnosed with a low-grade form of prostate cancer to see what happened to them. The study authors note that this type of low-grade cancer is "associated with a small chance of cancer-related death."

Of the 477 men with low-grade cancer, 244 opted for immediate treatment, with the majority undergoing surgery to remove the prostate gland, while 210 went for active surveillance. The active surveillance group had PSA tests and rectal exams every six months and repeat biopsies within a year of initial diagnosis. Additional biopsies occurred every two to four years, the authors said.

In the end, 30 per cent of the men in the active surveillance group underwent treatment. Most of those patients underwent treatment because their cancer was reclassified as a higher-risk form of the disease.

Overall, the number of men who underwent active surveillance also rose over time, going from 32 per cent in 2008 to 67 per cent in 2013.

"I don't think PSA is going to go away. It's a very effective test," said Dr. Stuart Edmonds, vice-president of research, health promotion and survivorship with Prostate Cancer Canada.

But not everyone interprets the study results as a vindication of the PSA test. Dr. James Dickinson, professor of family medicine and community health sciences at the University of Calgary, said low-grade prostate cancer rarely progresses to the point where it is a significant health risk. And in the meantime, those men in the "active surveillance" group who undergo repeat PSA tests, rectal exams and biopsies over the course of several years have to deal with unnecessary anxiety and stress, he said.

Dickinson, who is also a member of the Canadian Task Force on Preventive Health Care, said doctors should stop using PSA testing as a screening mechanism for prostate cancer. Researchers need to develop better ways of identifying those cases of prostate cancer that represent a real threat to men's health and the flawed PSA test is not the right way to do it, he said.

"Eventually, we will find a way to identify the real cancers, the ones that do need treatment and not cause harm to the very large number of men who have what sort of looks like cancer but isn't going to cause trouble in their lifetime," Dickinson said.

The Canadian Cancer Society recommends men over 50 talk to their doctors about their personal risk of developing prostate cancer and the risks and benefits of the PSA test.