Do the results of recent randomized trials justify the recent U.S. recommendation against yearly measurement of prostate-specific antigen (PSA) as a screening test for prostate cancer? That's the topic of debate in a special "point/counterpoint" section in the April issue of Medical Care. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.
The recommendation against routine PSA measurement relies too heavily on randomized trial data, according to an article by Ruth Etzioni, PhD, of Fred Hutchinson Cancer Research Center, Seattle, and colleagues. They argue that modeling studies provide a truer picture of the long-term benefits of PSA screening. But Dr Joy Melnikow of University of California, Davis, and colleagues disagree, asserting that randomized trials provide a sufficient level of certainty to recommend against PSA screening.
Point: Short-Term Trials Don't Reflect Long-Term Risk
Last year, the U.S. Preventive Services Task Force recommended against routine PSA measurement to screen for prostate cancer. The recommendation was mainly based on two recent studies—one conducted in Europe and one in the United States—in which men were randomly assigned to annual PSA screening or no screening. Both studies concluded that annual screening did not reduce the risk of death from prostate cancer.
But randomized trials have important limitations as a basis for screening policies, according to Dr Etzioni and colleagues. They note that screening trials generally provide short-term results, in contrast to the long-term results generated by population-wide screening programs. They argue that taking the randomized trial data at face value "misrepresents the likely long-term population impact of PSA screening (relative to no screening) in the United States."
Dr Etzioni and coauthors discuss the results of modeling studies that give a different picture of the benefits of PSA screening. Based on those models, screening may explain 45 percent of recent declines in U.S. deaths from prostate cancer, while changes in treatment account for 33 percent. When the randomized trial data are extrapolated to the U.S. population over the long term, the absolute reduction in deaths attributed to screening appears at least five times greater than in the original trial reports.
Modeling studies also suggest a lower rate of overdiagnosis—screening detection of slow-growing prostate cancers that otherwise would have caused no harm—than reported in the trials. Dr Etzioni and colleagues conclude, "With a disease whose hallmark is a lengthy natural history, the harms of developing cancer screening policies based primarily on limited-duration screening trials may well outweigh the benefits."