A recent study led by researchers at Johns Hopkins University has found evidence that plasma levels of C-reactive protein (CRP) are elevated in people who later develop colon cancer. Although some have interpreted these findings as an indication that the CRP test can be used to screen individuals for colon cancer, current research does not support such a conclusion.

CRP is a protein made by the liver that is often the first evidence of inflammation or infection in the body. Abnormally high levels of CRP alert medical professionals that further testing may be necessary to determine the cause of the elevation. For example, increases in CRP have been associated with increased risk of heart disease and a related test, hs-CRP, is being increasingly used in risk evaluation for this disease. CRP also is elevated in a number of other conditions, including inflammatory diseases like rheumatoid arthritis and lupus, stroke, and macular degeneration; consequently, CRP tests are not specific enough to be considered diagnostic for any particular disease.

In the Hopkins study, medical records from the CLUE II study in Maryland were used to identify patients with colorectal cancer. Plasma CRP levels from 172 patients who developed colorectal cancer within 11 years of their initial blood draw were compared to those from patients who did not develop the cancer over that same time period. Results indicated that the highest concentrations of CRP were found in those who subsequently developed colon cancer as compared with patients in a control group and that those individuals in the highest quartile of CRP had 2.5 times the risk of developing the disease than those in the lowest quartile. These findings suggest that inflammation may have a role in the development of colon cancer.

Because there are multiple conditions in which CRP is elevated, CRP testing alone is not useful as a screen for colon cancer. However, the findings from this study do provide new information that will be useful as researchers continue to investigate the mechanism by which this disease develops, which could potentially lead to better prevention measures, screening tools, and treatments.