NEW YORK (Reuters Health) - Annual screening for prostate cancer doesn't cut men's chances of dying from the disease, according to the latest results of a large screening trial.
Comparing men who were screened each year with so-called PSA tests, for prostate specific antigen, or rectal exams to those who received their usual care, researchers found that more men in the screening group had been diagnosed with prostate cancer after 13 years -- but there was no difference in how many had died from it.
The results support a previous report by the same researchers that found no difference in deaths seven to 10 years after the screening program started.
They are also consistent with recent draft guidelines from the U.S. Preventive Services Task Force recommending that average-risk men not undergo regular PSA screening, according to a researcher who worked on the study.
"Men, if they're considering screening, should be aware that there's a possibility that there's little or no benefit (and) that there certainly are harms to PSA screening," said study co-author Philip Prorok, from the National Cancer Institute in Bethesda, Maryland.
Those harms include catching and treating small cancers that never would have been detected or caused men any problems, Prorok told Reuters Health.
According to the Centers for Disease Control and Prevention, about 223,000 men were diagnosed with prostate cancer in the U.S. in 2007, the most recent year with available data, and 29,000 died from the disease.
The new findings are from a national study examining the effect of screening for prostate, lung, colon and ovarian cancers.
The data come from close to 77,000 middle-aged and older men, who between 1993 and 2001 were randomly assigned to a regular screening program with six years of annual PSA blood testing and four years of rectal exams, or to their usual care.
For some men, that usual care included cancer screening. The researchers estimated that men in the comparison group received about half as much screening as those enrolled in the annual screening program.
Thirteen years after the start of the study, 4,250 men who'd undergone annual screening had been diagnosed with prostate cancer, compared to 3,815 not in the screening program.
That worked out to a 12 percent increase in the number of cancers diagnosed with regular screening, Prorok and his colleagues reported Friday in the Journal of the National Cancer Institute.
However, there was not a clear difference in the number of men who died of prostate cancer over that time period: 158 in the annual screening group and 145 in the comparison group.
That was still the case when the researchers looked specifically at older or younger men, and those that did or didn't have other diseases.
Prorok said that because the number of cancers diagnosed in the usual care group never caught up with those found through regular screening, the PSA tests and exams that followed likely picked up some cancers that otherwise wouldn't have caused symptoms or threatened men's health.
"Somebody who is never going to suffer adverse effects of a disease, if you label them with cancer, you're kind of doing them a disservice," said Dr. Philipp Dahm, a urologist from the University of Florida in Gainesville, who has studied prostate cancer screening but wasn't involved in the new report.
And treatment, whether or not it's necessary, can come with side effects such as incontinence and impotency, he added.
Dahm said that one limitation of this study is that because men in the usual care group were allowed to get cancer screening, it can't compare prostate cancer outcomes in men with annual screening and those who never get PSA tests.
Dr. Scott Eggener, a urologic cancer specialist from the University of Chicago Medical Center not involved in the study, said that was a serious flaw.
"It ends up being a study of intensive screening versus fairly intensive screening," he told Reuters Health. "You can't really make sense of it."
A large European study that may have provided a clearer comparison did suggest the tests are helpful at preventing deaths from prostate cancer, but the researchers said it had its own set of limitations.
When it comes to annual PSA testing, Prorok said, "There's no absolute clear answer here, but I think it's important that men become fully informed before they decide what to do."
"I think in the future it will be wrong for physicians just to add this to the labs. It's important that physicians and patients talk about the value and the potential downsides of this test," he told Reuters Health.
"I'm sure it does good for many patients, but it has the risk for potential harm. Men just need to know what they're getting themselves into."
SOURCE: bit.ly/AoyC3I Journal of the National Cancer Institute, online January 6, 2012.