Leading doctors have called for an independent reappraisal of a powerful prostate cancer study after a review found it may have misled men into believing PSA screening tests can save lives.
Every year millions of men have a prostate specific antigen (PSA) blood test in the belief it will detect early-stage prostate cancer, giving them the best chance at swift and potentially lifesaving treatment.
The pivotal research underpinning this claim is the European Randomised Study of Screening for Prostate Cancer, which randomly allocated 162,000 men aged in their 50s and 60s to either a screening or control group. Those screened were given PSA blood tests every four years.
After 11 years, the study concluded that the screened men had a 21 per cent reduced chance of dying from prostate cancer.
However, a new Australian review of the study, published this month in the Journal of the National Cancer Institute, has cast serious doubt on its results after finding a large disparity in the treatments given to those diagnosed with prostate cancer in the control group compared with those who were screened.
It found that men with prostate cancer in the control group were twice as likely as those in the screening group to receive androgen-deprivation therapy alone – a hormone treatment that is known to produce inferior outcomes for early-stage cancer and may even encourage some cancer cells to grow.
The apparent bias appears to have increased the chances of earlier death for men in the control group rather than reducing the chances of death for those receiving PSA screening.
The review was conducted by adjunct clinical associate professor Ian Haines, an oncologist at Monash University and Cabrini Hospital, and Dr George Miklos, a scientist who heads Secure Genetics in Sydney. It found that if only 11 men in the control group had not died of prostate cancer, there would have been no lifesaving effect attributed to screening in the European study.
"The picture that emerges from the European trial is a sobering one. The claim of lives saved by screening and treatment is so flawed as to be clinically meaningless," Dr Miklos said.
PSA tests are controversial because they can cause "overdiagnosis" of prostate cancer that is so slow-growing it was never going to cause men harm. It is now estimated that for every man thought to be saved by the test, another 12 to 47 will be diagnosed with cancer that will not kill them. Many will have surgery and other interventions that can lead to sexual impotence and incontinence.
In response to the Australian review of the European study, chief medical officer of the American Cancer Society Otis Brawley called for the European researchers to provide their raw data for independent analysis. Dr Brawley’s call was backed by two public health experts at Bond University and Sydney University, professors Chris Del Mar and Bruce Armstrong.
Two of the researchers who worked on the European study, Professor Fritz Schroder and Dr Monique J. Roobol, would not say if they planned to release their raw data for independent analysis, but Professor Schröder said he disagreed with the Australian findings. In an email, Dr Roobol said all their data had been "analysed with great care".
A spokesman for the Urological Society of Australia and New Zealand, Shomik Sengupta, said he did not think higher rates of hormone therapy had caused higher death rates in the study's control group. He said the European study and others suggested PSA testing saved lives and that urologists were doing their best to limit the potential harms associated with the tests.
‘‘Men continue to die from prostate cancer and PSA testing offers an opportunity to find the disease at an earlier stage and address it,’’ he said.