C-reactive protein (CRP) -- a marker of inflammation circulating in the blood already associated with increased risk of heart disease -- can also be used to identify a person's risk of developing colon cancer, according to a Johns Hopkins study.
Results of the study, published in the Feb. 4 issue of The Journal of the American Medical Association, showed that over an 11-year period, people with higher levels of CRP in their blood (a median of 2.44 milligrams per liter) were more likely to develop colorectal cancers than those with low levels of CRP (a median of 1.94 mg/L).
"Higher levels of C-reactive protein are linked to an increased risk of several apparently distinct, chronic diseases: heart disease, stroke, diabetes, and now colon cancer," says Thomas "Tate" P. Erlinger, M.D., M.P.H., lead author of the study and an assistant professor of medicine at Hopkins. "However, it's not clear yet how or whether measuring C-reactive protein would fit into current screening and prevention strategies for colorectal cancer. Further studies should help answer these questions and help clarify the mechanism by which inflammation increases the risk of cancer."
Erlinger and colleagues studied the records of 22,887 adults who participated in the CLUE II study, conducted in Washington County, Md., looking to identify those who developed colon or rectal cancer. In the CLUE II investigation, named for its campaign, "Give Us A Clue to Cancer and Heart Disease" and started between May and October 1989, study volunteers provided a blood sample and completed a brief health questionnaire. They since have been followed by additional questionnaires and tracking data.
Comparing the CLUE II medical records with the Washington County and Maryland State cancer registries, the Hopkins team noted 172 people who were diagnosed with either colon or rectal cancer following their initial date of blood draw through December 2000. Of these, 131 had colon cancer and 41 had rectal cancer. Researchers then compared the health records of each of these individuals with those of up to two healthy volunteers who joined the study at the same time, using the healthy volunteers as a control group.
Median CRP levels at baseline were higher among people who subsequently developed colon cancer (2.69 mg/L) than among those who remained free of disease (1.97 mg/L). By contrast, CRP concentrations were not significantly different between cases of rectal cancer (1.79 mg/L) and the controls (1.81 mg/L).
The study also found that:
* The odds of developing colorectal cancers increased progressively with higher concentrations of CRP. Overall, people in the highest fourth of CRP had twice the risk of developing colorectal cancer, and 2.5 times the risk of developing colon cancer, as those in the lowest fourth.
* Among nonsmokers, those in the highest fourth of CRP were 2.5 times as likely to develop colorectal cancer, and 3.5 times as likely to develop colon cancer, as those in the lowest fourth.
* Those who had taken either aspirin or nonsteroidal anti-inflammatory agents within the 48 hours prior to blood draw had a reduced risk of colorectal cancer.
* The association of inflammation with colon cancer was unrelated to diabetes, going against the belief that diabetes acts as the mediator between inflammation and cancer risk.
Erlinger notes that while these results should apply to the general population, most of the study population was Caucasian, so further studies should look at a more diverse group.
The study was supported by grants from the Maryland Cigarette Restitution Fund, the National Institutes of Health, and the American Institute for Cancer Research. Co-authors were Elizabeth A. Platz and Kathy J. Helzlsouer of Hopkins and Nader Rifai of Harvard Medical School.
Materials provided by Johns Hopkins Medical Institutions. Note: Content may be edited for style and length.
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