Annual screening for prostate cancer with the PSA (prostate-specific antigen) blood test doesn’t reduce men’s risk of dying from the disease, according to updated findings from a large, multi-centered study published last Friday in the Journal of the National Cancer Institute (JNCI).
These findings support the controversial draft recommendation issued in October by the United States Preventive Services Task Force (USPSTF) that the PSA blood test not be used routinely for prostate screening.
“This study and other results that are coming along, as well as other recommendations, are shedding light on the fact that more testing, more treatment may not always be a good thing,” said Dr. Timothy Wilt, a member of that governmental task force and a co-director of the Minnesota Agency for Healthcare Research Quality (AHRQ) Evidence-based Practice Center, in a phone interview last week. (Wilt was not involved in the JNCI study.)
“The PSA blood test is very unlikely to help men live longer or live better for at least the next 15 or 20 years, and has serious harms related to it,” he added. “Those harms occur frequently, early, and may persist.”
Among those harms are pain, infection and bleeding from the biopsies that are done when an elevated PSA level is detected. In addition, Wilt said, routine PSA tests are causing many men to undergo unnecessary treatments for slow-growing cancers that are not life-threatening. Such treatments can lead to incontinence, impotence and even premature death.
Longer follow-up made no difference
Among the data that Wilt and the other USPSTF members used to make their prostate-cancer screening recommendation were those from the Prostate, Lung, Colorectal and Ovarian Cancer Screening (PLCO) Trial — the study whose updated findings were published Friday. Its researchers, which include a team right here in Minnesota, enrolled some 77,000 American men aged 55 to 74 and randomized them into two groups: those who received annual PSA screening and those who received “usual care,” or screening only when symptoms appeared.
In 2009, the PLCO trial reported that although more cancers were found in the PSA-screening arm of the study, the death rates for the two groups were the same. The study was immediately criticized, however, for including only 7 to 10 years of data. Prostate cancer is slow growing, the critics said, and therefore the men needed to be followed for a longer period of time.
The new JNCI paper does just that. It reports on outcomes through 13 years. Once again, the data show a statistically significant (12 percent) relative increase in the incidence rate of prostate cancer among the group of men who received annual PSA tests, but they show no differences in the death rates between the two groups.
“For the type of screening that we did, on the schedule we did, with the type of follow-up that occurred, there is no evidence that screening does any good in reducing mortality for prostate cancer,” said Timothy Church, one of the principal investigators for the PLCO trial and a co-author of the JNCI study. Church is a biostatistician and professor of environmental health sciences at the University of Minnesota’s School of Public Health.
The finding wasn’t a surprise, “but it was a disappointment,” Church said. Further crunching of the numbers may turn up subsets of men who would benefit from screening, but so far the evidence for those subsets is unconvincing, he added.
Prostate cancer takes the lives of about 30,000 men each year in the United States. The death rate has fallen in recent decades — a point often used in support of routine PSA screening. But the decline in the death rate is more likely due to improved treatments than to PSA screening, write Church and his co-authors in the study.
Debate will likely continue
Will this study’s results end the controversy over routine PSA screening? Probably not — at least not right away.
“I think prostate cancer screening will continue to be an area of great controversy,” said Wilt. “It is an extraordinary difficult general concept to think that a blood test can’t be beneficial.”
Church agrees. “There’s a controversy,” he said, “but I think it’s mostly driven by the true believers who believed before looking at the evidence that prostate cancer screening was beneficial and are not swayed by actually looking at trials. You have to keep in mind that prostate cancer screening went ahead long before there was any evidence of its efficacy. Starting in the ’90s, urologists started pushing the idea of prostate cancer screening using PSA because it was so simple and so easy. They were convinced based on just logic that if you find it early, you can treat it, and you’ll do some good. So they went ahead without doing the careful studies that we’re doing now.”
“There is a large body of people who sort of staked their reputation on this,” he added. “So it’s hard for them to back down based on a one or two large studies because they bought into it so solidly and so early on.”