Canadian Study is First to Show Screening Reduces Prostate Cancer Deaths
An eight-year large-scale randomized study, begun in 1988, was designed to evaluate the survival benefit of prostate cancer screening. The study randomly divided 46,193 men aged 45 to 80 into those who would be screened and those who would not. Those screened received a PSA (prostate-specific antigen) test and digital rectal examination at the first visit and transrectal echography of the prostate if PSA or digital rectal examination was abnormal. At annual follow-up visits, a PSA test was performed, followed by digital rectal examination and transrectal echography if PSA was abnormal (about 3.0 ng/ml, or an increase of more than 20% in one year).
137 deaths due to prostate cancer occurred in the 38,056 unscreened men, while only 5 deaths were observed among the 8,137 screened men, corresponding to 48.7 deaths/100,000 men-years for the unscreened group, and 15.0/100,000 men-years in the screened group, or a 69% decrease in deaths from prostate cancer in the group of men who were screened and received early treatment.
The authors conclude that screening based largely on PSA test results is a highly efficient means of diagnosing localized prostate cancer at a reasonable cost, and that it results in an important reduction of cancer death. However, other experts caution that the mechanism of patient recruitment may have biased the study, and confirmatory data will be required before this approach becomes a national standard.
"It appears that prostate cancer mortality may be significantly reduced by screening and early intervention," said Derek Raghavan, MD, PhD, of the University of Southern California Norris Comprehensive Cancer Center. "However, we still need to know more about whether the study's methodology and patient selection process influenced the results, as this is a highly controversial issue. It would be premature to set national guidelines based on any one study, especially as routine implementation of screening asymptomatic patients will be very expensiveto the general community. This is encouraging research that needs to be confirmed."