Updated European Prostate Cancer Screening Trial Data Show Little Change in Risk ReductionAfter 11 years of follow up, results from a large European clinical trial continue to show a reduced risk of death from prostate cancer associated with prostate specific antigen (PSA) screening. The findings, from the European Randomized Study of Screening for Prostate Cancer (ERSPC) trial, show a 21 percent relative reduction in prostate cancer mortality among men who underwent routine PSA screening compared with men who did not—the same risk reduction previously reported after 9 years of follow-up.
Consistent with the earlier results, screening was also associated with important harms, Dr. Fritz Schröder of Erasmus University Medical Center and his colleagues reported March 15 in the New England Journal of Medicine. About half of those diagnosed on the basis of PSA screening were overdiagnosed—that is, diagnosed with prostate cancers that likely would never have threatened their lives.
Overall, the researchers found that 1,055 men would need to be invited for screening and 37 cancers would need to be detected to prevent one death from prostate cancer.
With approximately 182,000 participants, the eight-country ERSPC trial consortium is the largest randomized study of PSA screening for prostate cancer ever conducted. Earlier this year, 13-year follow-up results were published from the second-largest trial, the NCI-funded Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial of 77,000 men. In the PLCO trial, annual PSA screening did not reduce the risk of dying from prostate cancer. Screening did lead to substantial rates of overdiagnosis but lower than those in the ERSPC trial.
The conflicting results have been attributed to a number of key differences between the trials, wrote Dr. Anthony Miller of the University of Toronto in an accompanying editorial. The two trials used different PSA scores as a cutoff point and screened men at different intervals. The PLCO trial also had a substantial amount of “contamination”—more than half of men in the PLCO control arm underwent screening outside the trial. In addition, he pointed to evidence that there may have been different prostate cancer treatment in the screened versus control arms of the ERSPC study.
“We are left with an unsatisfactory situation, in which many practitioners will think there are insufficient data to recommend abandoning PSA screening for prostate cancer,” Dr. Miller wrote. Because the PLCO results are more applicable to clinical practice in the United States, Dr. Miller said it would be “advisable” to follow the recent draft recommendations of the U.S. Preventive Services Task Force, which advise against PSA screening for prostate cancer among men considered to be at low risk of the disease.