Testing not a major factor in prostate cancer mortality

29 September 2009

Death from prostate cancer does not vary greatly between men who undergo annual prostate-specific antigen (PSA) screening and those who do not, according to an investigation of PSA outcomes.

"A Model of Prostate-Specific Antigen Screening Outcomes for Low- to High-Risk Men" was published in the Archives on Internal Medicine today. Dr Kirsten Howard from the University of Sydney's School of Public Health was the paper's lead author.

PSA screening involves testing the levels of a prostate specific antigen with a blood test. Elevated levels of that protein can sometimes indicate the presence of prostate cancer. An elevated PSA level usually leads to more invasive investigation and treatment including biopsies, radiation and prostatectomies.

The paper compares diagnosis and mortality outcomes of men who undergo annual PSA tests with those who did not take the tests.

"Unsurprisingly, we found men who test for prostate cancer had a higher rate of diagnosis," says Dr Howard. "But mortality rates from prostate cancer don't decrease significantly for this group.

"Older men, and those whose close family members had the disease, experience a slightly lower mortality rate from prostate cancer if they take regular tests. But the difference among those aged between 40 and 50 or who are at low risk is statistically insignificant."

Dr Howard says the high rate of diagnosis, when measured against the relatively low mortality rates, indicates men with PSA-detected cancer may often undergo therapies for clinically insignificant cancers.

"This is no small thing when you consider some of the side effects of further testing and treatment. Biopsies can cause haemorrhaging and infections while treatment carries with it the risk of impotence and/or incontinence.

"Furthermore, about a fifth of low-risk men will experience a false positive test in 10 years of screening. So some men will experience undesirable lifestyle changes when they don't even have prostate cancer."

Dr Howard says the paper does not suggest that men should not bother with PSA testing. "This research was done to make people better informed about the pros and cons of the test. We want people to weigh up the risks and benefits and discuss them with their doctor before deciding about testing and treatment. In the end, much of the choice comes down to one's individual values."

The paper does not make public policy recommendations but Dr Howard says its findings may cause some to question whether a widespread PSA testing programme was the best use of public health funds.

Associate Professor Alex Barratt from the School of Public Health, and Dr Manish Patel and Dr Graham Mann from the Sydney Medical School co-wrote the paper.

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