Screening for prostate cancer using the prostate-specific antigen (PSA) test is controversial, but stopping this screening could result in many more cases of advanced disease, a new study suggests.
Researchers analyzed information from the time before and after PSA testing became widespread, and found that screening using the PSA test prevents an estimated 17,000 cases of advanced prostate cancer in the United States each year. The average survival rate of men with advanced prostate cancer that has spread to other parts of their body at diagnosis is one to two and a half years, the researchers said. In contrast, nearly 100 percent of men who are diagnosed with prostate cancer at an early stage, before it has spread to other areas, are alive five years later, according to the American Cancer Society.
The findings add to the recent debate over prostate cancer screening.
Last year, an influential organization called the U.S. Services Preventive Task Force (USPSTF) recommended against prostate cancer screening altogether, saying its harms outweigh its benefits.
Recent studies on the topic have also had conflicting results, with some suggesting prostate cancer screening saves lives, and others finding no benefit.
The researchers say their new findings should be taken into consideration when creating PSA screening recommendations.
“There are trade-offs associated with the PSA test, and many factors influence the disease outcome,” said study researcher Dr. Edward Messing, chairman of urology at the University of Rochester Medical Center. “And yet our data are very clear: not doing the PSA test will result in many men presenting with far more advanced prostate cancer.”
The study is published online today (July 30) in the journal Cancer Epidemiology Biomarkers & Prevention.
Preventing advanced prostate cancer
Messing and colleagues reviewed data from the largest cancer registry in the U.S. for the years 1983 to 2008. Prior to 1986, PSA screening in men was not routine.
Based on the incidence of advanced prostate cancer in the mid-1980s, the researchers estimated that there would have been about 25,000 cases of advanced prostate cancer in 2008, had PSA screening not been done. But the actual number was about 8,000 cases, or three times less than expected.
The biggest reduction was seen in cancer cases in older men, particularly in those ages 80 to 85.
The study found only an association, not a cause-effect link between screening and fewer prostate cancer cases. It's possible factors other than PSA testing were responsible for the decrease in cases of advanced disease, although the researchers took into account participants' ages and ethnicities, two of the strongest risk factors for prostate cancer.
The researchers also pointed out that finding cancer earlier does not always translate into better survival. But in general, they concluded, PSA testing reduced the incidence of advanced disease.
Window of opportunity
“The USPSTF will be criticized for not having done analysis such as this,” Dr. Martin Sanda, director of the Prostate Center at Beth Israel Deaconess Medical Center in Boston, said of the study findings.
The task force based their recommendations mainly on one large, yet flawed, study, Sanda said.
The new findings agree with earlier research that estimated there would be about 30,000 more deaths from prostate cancer each year without screening. “Studies like this provide us a window of opportunity to not let that happen,” Sanda said.
Dr. Louis Kavoussi, chairman of urology at North Shore-Long Island Jewish Health System, agreed the main reason for the reduction in advanced cases of prostate cancer is PSA testing.
While men who have been screened for prostate cancer can end up receiving treatment they don't need, Kavoussi said, the screening test itself can't be blamed for this.
“The problem isn’t prostate cancer screening, it's what you do if you detect prostate cancer,” Kavoussi said.
After undergoing screening, men may receive unnecessary biopsies and treatments, which come with a risk of erectile dysfunction and loss of urinary control.
Doctors need to get better at knowing when to wait, and when to being prostate cancer treatment, Kavoussi said. Men should speak with their doctor about whether they should receive PSA testing, Kavoussi said.
Pass it on: Eliminating prostate cancer screening could result in thousands of more cases of advanced disease each year, researchers say.
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