Cancer Screening Trial Shows No Fewer Deaths from Annual Prostate Cancer Screening
Consecutive annual screenings for prostate cancer led to more diagnoses of the disease, but no fewer prostate cancer deaths. That’s according to a major new report from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial.
“This report, alongside data from a large, international European study also being published today, indicates the need for continued follow up on the benefits of prostate cancer screening,” said Dr. E. David Crawford, head of Urologic Oncology at the University of Colorado Denver’ School of Medicine and principal investigator for the University of Colorado Cancer Center’s arm of the study. “As we continue to access our work and collect more information, men should choose to know their PSA results and know to choose appropriate follow up.”
PLCO is a large-scale clinical trial, sponsored and run by National Cancer Institute’s Division of Cancer Prevention. The study began in 1992 to determine whether certain cancer screening tests can help reduce deaths from prostate, lung, colorectal and ovarian cancer. Nearly 155,000 women and men between the ages of 55 and 74 have joined the PLCO trial. Screening of participants ended in late 2006 but follow-up will continue for several more years. Results appear online March 18, 2009, in the New England Journal of Medicine, to coincide with presentation of the data at the European Association of Urology meeting in Stockholm, Sweden. The print version of the results will appear in the March 26, 2009 issue.
Crawford, who is founder and chairman of the Prostate Conditions Education Council, applauded the participation of 13,165 Coloradoans in this long-term trial.
“We would be unable to ever answer these important questions about cancer screening without them,” he said.
Nationwide, 76,693 men participated in the PLCO trial. Participants were randomly assigned to the screening group—they underwent six annual prostate-specific antigen (PSA) tests and four annual digital rectal exams (DRE)—or the “usual care” control group, which received no recommendations for screening.
Of the men screened annually, 85 percent had PSA tests and 86 percent had DREs. Men in the usual-care arm sometimes also had these tests due to growing public acceptance of such screening.
Screening by PSA in the usual-care group increased from 40 percent at the beginning of the study to 52 percent by the last screening year. DRE screening ranged from 41 percent initially to 46 percent by the last screening year. Men in the screening arm were referred to their usual health care provider for follow-up testing if their PSA level was higher than acceptable levels or if the DRE found an abnormality.
The PLCO report includes data for all participants seven years after they joined the trial. For 67 percent of participants, the data extends 10 years after they joined the trial. Important findings include:
- At seven years, 22 percent more prostate cancers were diagnosed in the screening arm (2,820 men vs. 2,322 in the usual-care group). This excess is continuing to be observed in data collected up to 10 years (currently a 17 percent excess, 3,452 men vs. 2,974 men).
- The vast majority of men in both groups who developed prostate cancer were diagnosed with relatively early stage II disease (out of IV stages, of which IV is late stage), and the number of later-stage cases was similar in the two groups. However, using the Gleason scoring system, which assesses tumor aggressiveness, men in the usual-care group had more prostate cancers that fell into the Gleason 8 to 10 range, which marks them as more aggressive. The smaller number of men with prostate cancer with a Gleason score of 8 to 10 in the intervention group may eventually lead to a mortality difference between men in the two groups but data analyzed so far have not shown such a difference.
- Men in both groups who were diagnosed with prostate cancer at the same stage received similar treatments for their disease. This reflects the PLCO study design policy of not mandating specific therapies.
- At seven years, 50 deaths were attributable to prostate cancer in the screening group and 44 deaths were attributable in the usual-care group. Through year 10, there were 92 prostate cancer deaths in the screening group and 82 in the usual-care group. The difference between the numbers of deaths in the two groups was not statistically significant. Thus there was no detectable mortality benefit for screening vs. usual-care.
“Together, these studies reinforce the importance of communication between patients and physicians,” Crawford said. “When it comes to prostate cancer, knowledge is power. Screening provides vital information for patients and doctors that helps them decide whether it is appropriate to pursue additional testing and treatment.”
The PLCO data are being made public now because the study’s Data and Safety Monitoring Board (DSMB), an independent review committee that meets every six months, saw a continuing lack of evidence that screening reduces death due to prostate cancer. The DSMB also heard the suggestion that screening may cause men to be treated unnecessarily. The DSMB also supports continued follow up of all participants so that every participant is tracked for at least 13 years from entry into the trial.
A Q&A on the prostate screening results from the PLCO is available online.
The University of Colorado Cancer Center is the Rocky Mountain region’s only National Cancer Institute-designated comprehensive cancer center. NCI has given only 40 cancer centers this designation, deeming membership as “the best of the best.” Headquartered on the University of Colorado Denver Anschutz Medical Campus, UCCC is a consortium of three state universities (Colorado State University, University of Colorado at Boulder and University of Colorado Denver) and five institutions (The Children’s Hospital, Denver Health, Denver VA Medical Center, National Jewish Health and University of Colorado Hospital). Together, our 400+ members are working to ease the cancer burden through cancer care, research, education and prevention and control. Learn more at www.uccc.info.