The recently released results of two large randomized trials suggest there are no big benefits from prostate cancer screening, and if anything, they are quite small, says a new report by US researchers. And an accompanying editorial goes so far as to suggest that while screening has doubled the risk of a diagnosis, it has done little to reduce the risk of death from prostate cancer.
The report appears in the online pre-print 29 June issue of CA: A Cancer Journal for Clinicians and is the work of Dr Otis W Brawley, of the American Cancer Society and Drs Donna Ankerst and Ian M Thompson, of the University of Texas Health Science Center at San Antonio.
Brawley and colleagues wrote that since prostate cancer affects many men as they age, the goal of screening should not be to find more cances but to reduce the risk of death from the disease, reduce the suffering it causes, or reduce the cost of treating and caring for patients who have it.
They said that the current state of prostate cancer screening fails to reach any of these suggested standards.
Neither the American Cancer Society nor any other major medical group recommends routine prostate cancer screening for men who are at average risk.
In the US, about 1 in 6 men will get prostate cancer at some point in their lives, and since the mid 1980s, the PSA (prostate-specific antigen) blood test has doubled the likelihood of a prostate cancer diagnosis.
The authors wrote however, that while prostate cancer deaths have also gone down over the same period, it is not clear whether this is due to PSA testing or other factors like better treatment.
The recent release of two large randomized trials suggests that “if there is a benefit of screening, it is, at best, small”, wrote the authors.
One study applied a computer model to the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) registries and estimated that 29 per cent of prostate cancers detected in white men and 44 per cent of those detected in black men were overdiagnosed.
The other study used a similar model on European data and estimated that the overdiagnosis rate there was about 50 per cent.
The authors suggest that men who are diagnosed with tumors that have little clinical significance undergo unnecessary diagnostic tests and treatment and are psychosocially harmed. They also have to put with the negative effect of being labelled a “cancer patient”, which can affect them economically.
On the public health monitoring front, overdiagnosis of prostate cancer has a big impact on the 5-year survival figures, causing confusion and failure to show the true progress of cancer control.
The authors recommend that:
“Methods to assess a man’s risk of prostate cancer, including those tools that integrate multiple risk factors, are now available and should be used in risk assessment.”
They also wrote that screening and assessment tools are improving, and there are also new ways to prevent the occurrence of prostate cancer, including the use of the drug finasteride, which is currently used to treat urinary symptoms that result from an enlarged prostate.
Brawley also wrote a separate editorial on prostate cancer screening with Dr Peter Boyle, of the International Prevention Research Institute in Lyon, France. They commented that:
“The real impact and tragedy of prostate cancer screening is the doubling of the lifetime risk of a diagnosis of prostate cancer with little if any decrease in the risk of dying from this disease.”
In 1985, before PSA was used in the US, an American man’s lifetime risk of being diagnosed with prostate cancer was 8.7 per cent, and the lifetime risk of dying from it was 2.5 per cent. In 2005, the lifetime risk of diagnosis shot up to 17 per cent, while the lifetime risk of dying has stayed at a low 3 per cent, they added, concluding that:
“Men should discuss the now quantifiable risks and benefits of having a PSA test with their physician and then share in making an informed decision.” Also, they urged that:
“The weight of the decision should not be thrown into the patient’s lap.”
“Screening for Prostate Cancer.”
Otis W. Brawley, Donna P. Ankerst, and Ian M. Thompson.
CA Cancer J Clin, published online before print June 29, 2009.
DOI:10.3322/caac.20026
“Prostate Cancer: Current Evidence Weighs Against Population Screening.”
Peter Boyle and Otis W. Brawley.
CA Cancer J Clin, published online before print June 29, 2009.
DOI:10.3322/caac.20025
Source: American Cancer Society.
Written by: Catharine Paddock, PhD