Annual prostate cancer screening trial shows no early mortality benefit

The prostate cancer screening tests that have become an annual ritual for many men don’t appear to reduce deaths from the disease among those with a limited life expectancy, according to early results of a major U.S. study involving 76,000 men.

Results from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial show that six years of aggressive, annual screening for prostate cancer led to more diagnoses of prostate tumors but not to fewer deaths from the disease. The study, led by School of Medicine researchers and conducted at 10 sites, appeared March 26 in the New England Journal of Medicine.

“The important message is that for men with a life expectancy of seven to 10 years or less, it is probably not necessary to be screened for prostate cancer,” said the study’s lead author and principal investigator, Gerald Andriole, M.D., professor of surgery.

But it’s too soon, he said, to make broad screening recommendations for all men based on the study’s initial findings.

“So far, only a minority of men enrolled in the PLCO study have died, so it may be premature to make generalizations about the ultimate results of the trial,” he said. “We don’t have enough data yet about the youngest men in the study — those in their 50s — and it may be that over time, we will, in fact, see a benefit from screening.”

Nearly 6,400 men are enrolled in the study at the School of Medicine. Robert Grubb III, M.D., assistant professor of surgery, is a collaborator and the study’s second author.

The PLCO trial began in 1992 with funding from the National Cancer Institute and was designed to determine whether prostate cancer screening reduces deaths from the disease. It involves men ages 55-74 who received either annual PSA blood tests and digital rectal exams or “routine care,” receiving screening tests only if their physicians recommended them. After seven to 10 years of follow up, deaths from prostate cancer were very low in both groups and did not differ significantly between the groups.

Health guidelines issued last year by the U.S. Preventive Services Task Force recommend against prostate cancer screening for men age 75 or older and concluded there is insufficient evidence to assess the balance of benefits and harms of prostate cancer screening in men younger than 75. However, the American Urological Association and the American Cancer Society recommend annual prostate cancer screening tests beginning at age 50 for most men.

More than 186,000 U.S. men will be diagnosed with prostate cancer this year, and nearly 29,000 will die from the disease, according to the National Cancer Institute. PSA blood tests, introduced in 1988, have increasingly been used as a screening tool for prostate cancer, despite a lack of evidence showing they reduce death rates from disease.

The controversy over prostate cancer screening has arisen because most men who undergo a biopsy for an abnormal PSA test do not have prostate cancer. For those who have cancer, the tumors generally grow so slowly that most men die of other causes. Furthermore, prostate cancer treatment can result in incontinence and impotence. However, some tumors can be aggressive, and the difficulty has been distinguishing aggressive cancers from those that are slow growing.

“We definitely need to find better ways to detect and treat aggressive tumors, those that are truly life-threatening, so that men with slow-growing tumors can avoid unnecessary treatments,” said Andriole, chief urologic surgeon at the Siteman Cancer Center.

The results are the first to detail death rates from prostate cancer among men in the PLCO study. The data are being made public because the study’s Data and Safety Monitoring Board saw a continuing lack of evidence that screening reduces deaths due to prostate cancer as well as the suggestion that screening may cause men to be treated unnecessarily. Investigators will follow patients for several more years to see whether annual screening eventually reduces prostate cancer deaths.

The trial involved 76,693 men who were randomly assigned to receive either annual PSA blood tests for six years and digital rectal exams for four years or routine care, which included physical checkups but no mandate for annual prostate cancer screenings.

The report includes data for all participants seven years after joining the trial and for 67 percent of participants 10 years after joining the trial.

At seven years, there were 22 percent more prostate cancer diagnoses in the men screened annually (2,820 men in the screening group versus 2,322 in the routine-care group). At up to 10 years, there were 17 percent more prostate cancer diagnoses in the screening group.

Deaths from prostate cancer did not differ significantly between the groups. Seven years after the screening began, there were 50 deaths from prostate cancer in the screening group and 44 deaths in the routine-care group. At 10 years, there were 92 prostate cancer deaths in the screening group and 82 in the routine-care group.

“My recommendation is that, for now, men with a life expectancy of more than seven to 10 years continue to be screened for prostate cancer,” Andriole said.

“On the other hand, screening is probably not necessary for elderly men and men with significant health issues. These men should talk with their doctors to decide whether they want to be screened because clearly there can be harmful side effects related to treatment, while for these men, there has been no demonstration that screening will prolong their lives,” he said.