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Study shows prostate cancer mortality rates unchanged by PSA testing
Published Tuesday, March 1, 2016 3:53PM MST
Last Updated Tuesday, March 1, 2016 7:12PM MST
Researchers at the University of Calgary are disputing the value of PSA screening and say testing increases the number of cases diagnosed but only minimally reduces mortality rates if at all.
The study assessed the effects of PSA testing and suggests that the decline in mortality rates from the disease is more likely due to the evolution of treatment.
PSA testing measures the amount of prostate specific antigen in the blood and high levels could indicate the presence of cancer.
The risk of developing the disease rises with age, especially in men over 75.
"Screening causes substantial increases in the number of men diagnosed with prostate cancer, especially before 70 years of age," said Dr. James Dickinson, from the University of Calgary and lead author of the paper. "However, most would never have known about it otherwise, and died of other causes at a normal age."
PSA testing was introduced in Canada in the early 90s and by 2008, Canada and countries that used the screening tool saw prostate cancer rates increase.
Researchers say treatments like surgery, chemotherapy and radiation cause harm because of the physical and mental toll on the body.
"Treatment is worthwhile for the five in 1000 men with cancers that would invade and kill, but not for the men with slow-growing cancers that do not: possibly over 120 per 1000," said Dickinson.
The research suggests that mortality rates from prostate cancer started to decline a couple of years before the widespread use of PSA tests after 1996 and that it continues to drop by about 3.25 percent yearly.
"This pattern of decline in mortality rates began to occur earlier and is greater than could possibly be expected even from the most optimistic evaluation of screening," said Dickinson.
The group then looked at other reasons for the decrease and noted similar patterns of diagnoses and death rates in countries that started using PSA testing early.
In European countries that put off using the test, an expected delay in increase of diagnoses was seen and the change in mortality rates was similar to that of countries using PSA tests.
"This suggests that the mortality drop is likely due to changes in patterns of treatment such as surgery, chemotherapy and radiation that occurred at that time in all these countries," said Dickinson. "There are also other possibilities such as changes in how deaths were reported."
Dickinson says the study shows most men who do not take a PSA test will likely never know they have cancer and that those who develop advancing cancer should be diagnosed and treated when symptoms occur.
The results of the study were published in the online edition of CMAJ Open on March 1.