Can CRP Predict Colon Cancer Risk?

Summarized by Robert W. Griffith, MD
May 7, 2004

Introduction

C-reactive protein (CRP) certainly seems to be the "test-du-jour". Originally developed to determine if there's an inflammatory process going on in the body, it's been used to predict the risk of coronary heart disease and heart attack, stroke, osteoarthritis, and, most recently, age-related macular degeneration (AMD). Now there's a report of plasma CRP levels in people who later develop colon cancer. It's published in the Journal of the American Medical Association, and we summarize it here.

What was done

In 1989 a group of 22,800 volunteers over 18 years old living in Maryland, USA, were enrolled into a long-term study. At enrollment they had blood taken and completed a health questionnaire. Eleven years later all cases of colon or rectal cancer were identified, through local Cancer Registries; there were 172 such cases.

To establish a control (non-cancer) group, up to two controls for each cancer case were selected who were known not to have cancer and who were alive at the cut-off point (December 2000). These control cases were matched to each cancer case according to age, sex, race, date of blood draw (plus or minus 2 weeks), and time since last meal before blood sampling.

A large number of possible factors that might be relevant were included in the analyses: smoking, weight, height, medications, hormone replacement therapy, and diabetes. In addition, follow-up questionnaires were used to establish if the participants had a history of inflammatory bowel disease before 1989, and whether they had a family history (parent, brother or sister).

What was found

In the colorectal cancer cases, there were 131 with cancer of the colon and 41 with cancer of the rectum. Their average age was 63½, and just over half were women.

Plasma CRP levels were significantly higher in the colorectal cancer cases, compared with their matched controls - averaging 2.44 mg/L for cancer cases and 1.94 mg/L for controls. The highest levels were found in those subjects who subsequently developed colon cancer - 2.69 mg/L vs. 1.97 mg/L for controls; there was no increase in the cases who later developed rectal cancer.

The risk of someone developing colorectal cancer increased with higher levels of CRP measured at baseline. And this risk was even greater in non-smokers than in smokers. On the other hand, use of either aspirin or a non-steroid anti-inflammatory drug (NSAID) was associated with a lower level of risk. Other factors that might have influenced the outcome were not found to change the relationship between CRP levels and colon cancer.

What this means

CRP levels are a 'marker' for inflammation in the body. The results of this study are therefore consistent with the concept that the risk of colon cancer is increased with inflammation. Supporting this view is the finding that use of anti-inflammatory drugs (aspirin, NSAIDs) was linked to a lower risk.

People with chronic inflammatory bowel disease, especially ulcerative colitis, are at increased risk of developing colorectal cancer. And CRP has again been established as a nonspecific marker of inflammation; it can therefore be used to help assess the benefits of a particular line of therapy in people at risk.

Source

• C-reactive protein and the risk of incident colorectal cancer. TP. Erlinger, EA. Platz, N. Rifai,  et al., JAMA, 2004, vol. 291, pp. 585--590

Related Links
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Do You Know Your CRP?
Unhealthful Diet Puts Women at Risk for Colon Cancer

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