A major European study has shown that blood test screening for prostate cancer saves lives, but doubts remain about whether the benefit is large enough to offset the harms caused by unnecessary biopsies and treatments that can render men incontinent and impotent.
The study, published in The Lancet (August 6, 2014), found that midlife screening with the prostate-specific antigen, or PSA, screening test lowers a man’s risk of dying of the disease by 21 percent. The relative benefit sounds sizable, but it is not particularly meaningful to the average middle-age man, whose risk of dying of prostate cancer without screening is about 3 percent. Based on the benefit shown in the study, routine PSA testing would lower his lifetime cancer risk to about 2.4 percent.
Despite the fact that some men —one out of every 781 men in the screening group — were helped by PSA testing in the European study, the study authors say the finding does not support the use of widespread screening. Instead, cancer experts say, the focus should be on screening men at high risk and working to identify nonaggressive cancers so men will not be unnecessarily treated for the disease.
“We know we are finding a substantial number of cancers, in the range of 30 to 50 percent, that would never do any harm and would not lead to death’’ said the study’s lead author, the urologist Dr. Fritz H. Schröder from Erasmus University Medical Center in the Netherlands. For every 27 cancers detected by PSA screening, only one man’s life would be saved.
“This overdiagnosis is unacceptable because it also leads to treatment,’’ Dr. Schröder said. “That’s why there is consensus worldwide, with very few exceptions, that the time has not come to recommend population-based screening.”
The findings, based on 13 years of data from a continuing randomized study of 162,000 European men, are certain to create confusion about the relative benefits and risks of the PSA test, which uses a blood sample to identify men at risk for prostate cancer. The test often puts men on a path of repeated biopsies and testing, and for some, treatment of a cancer that would have never caused a problem if left alone. In 2011, the United States Preventive Services Task Force concluded that healthy men should not be screened for prostate cancer, a finding that drastically changed the standard of care for middle-age American men who had grown accustomed to annual screenings.
The task force recommendation against PSA testing was based largely on 10 years of data from two major studies: the United States-based Prostate, Lung, Colorectal and Ovarian (P.L.C.O.) cancer screening trial of 77,000 men, and earlier results from the current study, the European Randomized study of Screening for Prostate Cancer. Additional data collected from the European trial since then has shown a slightly larger benefit over time as a result of screening, along with a still sizable risk of overdiagnosis and overtreatment.
“It’s always been a complicated story,’’ said Dr. Ian Thompson,the director of the cancer therapy and research center at the University of Texas Health Science Center at San Antonio, who wrote an accompanying editorial to The Lancet study. Dr. Thompson said that better diagnostic techniques, such as biopsies guided by magnetic resonance imaging tests, along with personalized risk assessment and more informed decision making by men and their doctors were a better way to use the PSA test than to screen every man of a certain age.
“The majority of men who get PSA screening will not benefit from it,’’ Dr. Thompson said. “If you do PSA testing in a more sophisticated, contemporary way, there may be the possibility of achieving the mortality reduction while reducing the morbidity impact.”
Neither the American study nor the European study are viewed as the final word on PSA testing. A flaw in the American study is that many men in the nonscreening group had already received a PSA test before the study began or later sought screening on their own, thus blunting any potential benefit from showing up in the data analysis.
The European study, which recruited men from 50 to 74 in eight countries, also has flaws. One concern is that the increase in survival among men in the screening group may stem from differences in the quality of treatment compared with men in the control group. In addition, there are puzzling differences when comparing the results from individual countries. For instance, men in Sweden showed a benefit while men in Finland, where the incidence and mortality rate of prostate cancer is similar, did not.
“I think this additional follow-up doesn’t change much,’’ said Dr. Gerald L. Andriole, the lead author of the United States-based study and chief of urology at Washington University School of Medicine in St. Louis. “I think there is a benefit to PSA testing, but unfortunately, we’ve been overdoing it, screening the wrong men, overtreating way too many men, and the benefit of screening is being outweighed by the side effects of overtreatment.”
Doctors say that for men who are confused about whether to get a PSA test, there is hope. New M.R.I. tests to guide targeted prostate biopsies may help find the most aggressive cancers that require treatment, thus identifying men who do not need to be treated.
“The trick is to take the complex nature of the information and provide it to men,” Dr. Thompson said. “A man who is fully informed may say ‘I understand’ and decide against the test, while another man who watched his father die of prostate cancer may want it.”
Written by Tara Parker-Pope for the New York Times, August 6, 2014.
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