July 1, 2010 -- Screening men for prostate cancer cut mortality rates by about half in a large study, researchers report.
The screening test under investigation is called a prostate-specific antigen (PSA) test, which measures blood levels of a protein produced by prostate gland cells and is a marker for prostate cancer. PSA is considered a controversial screening test because it can detect cancers that may not advance during a man’s natural life span, resulting in possible over-treatment and reduced quality of life.
These latest findings, published in the July 1 issue of Lancet Oncology, could shed new light on the potential benefits of PSA screening. Last year, the American Urological Association recommended that men begin undergoing prostate cancer screening at age 40 instead of age 50, the group’s previous recommendation. This revision was criticized by some prostate cancer experts because of concerns that extensive screening would lead to over-diagnosis of the disease and create unnecessary anxiety among patients.
PSA Test Cuts Prostate Cancer Deaths
In this study, Jonas Hugosson of the University of Gothenburg in Sweden and colleagues tried to determine whether the benefits of prostate cancer screening outweighed the risks. They randomly divided 20,000 men born between 1930 and 1944 into two groups; every two years, one group received the prostate-specific antigen test while the second group, known as the control group, did not undergo screening. If the PSA test result reached a predetermined abnormal level, the men underwent follow-up testing, such as digital rectal exams, prostate ultrasounds, and biopsies.
The researchers found that during 14 years of follow up:
- Prostate cancer was diagnosed in 11.4% of the screening group vs. 7.2% of the control group.
- Among men with detected prostate cancer in the screening group, 78.7% were diagnosed as a result of enrolling in the study.
- Among this 78.7%, a total of 231 men had their cancer detected during the first round of screening and 665 men had their cancers detected during subsequent rounds of screening.
- Cancers were detected on average earlier in the screening group; advanced prostate cancer was detected in 46 patients in the screening group vs. 87 in the control group.
The authors note that a great deal of screening needs to take place to avoid one death. Their statistical analysis showed that 293 men needed to be screened and 12 men needed to be diagnosed and treated to result in one less death from prostate cancer. The study is ongoing.
“The risk of over-diagnosis is less than previously reported, but still 12 men need to be diagnosed to save one life,” Hugosson and his colleagues said. “Among men participating in the study at or below age 60, the risk of prostate cancer death was notably low, with only a quarter of the expected rate of death from prostate cancer.”
The findings suggest the benefits of prostate cancer screening can outweigh the risks, they say.
“In this trial, prostate cancer screening was well accepted by the general population and can result in a relevant reduction in cancer mortality, greater than that reported in screening for breast or colorectal cancer,” the authors write. Nevertheless, “the benefit from PSA screening requires at least 10 years to take effect, it seems questionable to invite all men over the age of 70 years for PSA testing.”
PSA Test Not Perfect
This study follows another recent European study examining the pros and cons of prostate cancer screening. Known as the European Randomised Study of Screening for Prostate Cancer (ERSPC), it showed that during a shorter follow-up period of nine years a total of 1,410 men needed to be screened and 48 men had to be treated to save one life. That study also showed a 20% reduction in mortality over the course of a nine-year follow-up.
Prostate cancer is one of the leading causes of cancer death among men in the United States; every year, more than 28,000 men die from the disease and more than 203,000 men are diagnosed with the illness.
In an accompanying editorial, David E. Neal, at the University of Cambridge in England, says he’s cautiously optimistic about the results of this study. The findings, he writes, “show that in certain circumstances, PSA testing and early diagnosis reduces death from prostate cancer.” However, “it does not imply that PSA screening programs should now be introduced internationally.”
The next step, Neal writes, would be to do a better job at identifying men with intermediate and high-risk prostate cancers by looking at other markers that could improve the sensitivity and specificity of prostate cancer detection.
Jeffrey Karnes, MD, a urological surgeon at the Mayo Clinic in Rochester, Minn., tells WebMD that “PSA is not perfect,” but can still “potentially be a life-saving test.”
“This is a timely article,” writes in an email. “As the full ERSPC [study] matures, I also believe that it will show greater reduction and fewer men diagnosed to save one life. As everyone knows, there can be a long lead time with PSA screening [because it] detects cancers many years before detectable or symptomatic, and there is still a risk of over-diagnosis, perhaps cancer would not have caused problems or death. Nonetheless, this new study demonstrates that PSA screening in a population can be effective and reduce prostate cancer death.”