Science Fact or Science Fiction: The Discrepancy Between Prostate and Colorectal Cancer Screening
The ]]>prostate specific antigen (PSA) blood test]]> used to screen for prostate cancer has been the subject of some debate. Although it makes sense that PSA screening ought to reduce the risk of death from prostate cancer, that assumption has yet to be substantiated by evidence from clinical trials. Critics of PSA testing fear that because prostate cancer develops too late in life to become a serious health threat for most victims, increased screening may actually lead to invasive follow-up testing and surgery that may be more harmful than the cancer itself.
This is not the case for colorectal cancer screening. Numerous clinical studies have indicted that ]]>fecal occult blood testing (FOBT)]]> and flexible ]]>sigmoidoscopy]]> can reduce deaths from colon cancer. While the evidence for ]]>colonoscopy]]> is less conclusive, it’s similarity to sigmoidoscopy strongly suggests that it too has the potential to lower the risk of colorectal cancer mortality.
As is often the case, physicians’ recommendations and patients’ decisions do not often reflect the latest scientific evidence. It is not surprising, therefore, that a group of researchers from Dartmouth Medical School and the VA Outcomes Group, Department of Veterans Affairs Medical Center in White River Junction, Vermont found that on average American men have their prostates screened more than their colons or rectums. Their study was published in the March 19, 2003 issue of the Journal of the American Medical Association.
About the study
The researchers used data from the 2001 Behavioral Risk Factor Surveillance System (BRFSS), an annual telephone survey conducted by the Centers for Disease Control and Prevention. They included the results of surveys from 49,315 American men from across the nation aged 40 years or older who responded to at least one prostate or colorectal question.
In regards to prostate cancer screening, all participants were asked whether they had ever had a PSA test, how recently, and whether they had been diagnosed with ]]>prostate cancer]]> . Men who reported having a PSA test within the past year were considered up-to-date with their screening.
In regards to colorectal cancer screening, all participants were also asked whether they had had an FOBT, sigmoidoscopy, or colonoscopy and how recently. Men who reported having an FOBT test within the past year, or a sigmoidoscopy or a colonoscopy within the past five years were considered up-to-date with their colorectal screening.
Overall, men were more likely to have been screened for prostate cancer than for ]]>colorectal cancer]]> . As many as 75% of men age 50 and older had had a PSA test, as compared to only 63% of men in the same age group who had undergone screening for colorectal cancer.
Men were also more likely to be up-to-date with their prostate screening tests. Among men between the ages of 50 and 69 years of age, 54% were current with their PSA screenings as opposed to the 45% who reported being current with their colorectal screening.
How does this affect you?
The study found that men tend to opt for a screening test that is less likely to improve their chances of survival according to available scientific evidence. The researchers suggest several reasons why this may be the case. For example, a simple blood test is undoubtedly more appealing than the inconvenient or invasive tests required for colorectal screening. Also, the “get tested” media campaign for prostate cancer may have been more successful than that of the colorectal screening campaign. Finally, although the annual death rates for prostate and colorectal cancer are approximately the same, the incidence of prostate cancer is three times greater than that of colorectal cancer. This means that more men are likely to know a friend or relative with prostate cancer than with colorectal cancer, which in turn may create the perception that the threat from prostate cancer is greater.
In an effort to bring cancer-screening practices in line with the scientific evidence, the researchers encourage physicians to inform their patients of the known benefits of colorectal cancer screeening versus the unknown benefits of PSA testing. This is not to suggest that PSA testing is inappropriate and should be restricted or abandoned. Future studies may show that it does, in fact, save lives. Rather, the use of colorectal screening ought to be increased, especially since there is already science to back it up.
National Colorectal Cancer Research Alliance
American Cancer Society
National Cancer Institute
Prostate Cancer Research Institute
Sirovich BE, Schwartz LM, Woloshin S. Screening men for prostate and coloretal cancer in the United States: Does practice reflect the evidence? JAMA . 2003;289:1414-1420.
Last reviewed Mar 19, 2003 by ]]>Richard Glickman-Simon, MD]]>
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