Objective: Circulating C-reactive protein concentration has been associated with colorectal cancer in some studies. Whether C-reactive protein is associated with earlier steps in the natural history of this cancer has not been published (aside from an abstract). Thus, we evaluated the association between plasma C-reactive protein concentration and development of colorectal adenoma in a nested case-control study.
Methods: Colorectal adenoma cases (n = 135) and matched controls (n = 269) who had a negative sigmoidoscopy or colonoscopy were identified between baseline in 1989 and 2000 from among participants in the CLUE II cohort of Washington County, Maryland. Cases were confirmed by medical record review. Controls were matched with cases on age, sex, race, date of blood draw, time since last meal, and type of endoscopy. The odds ratio (OR) of adenoma was estimated from conditional logistic regression models.
Results: C-reactive protein concentrations were similar between colorectal adenoma cases and controls (median C-reactive protein, 1.31 vs. 1.38 mg/l; p = 0.13). The OR of colorectal adenoma among those in the highest fourth (>2.95 mg/l) of C-reactive protein concentration compared with the lowest fourth (<0.65 mg/l) was 0.61 (95% confidence interval, 0.29-1.25; p for trend = 0.25).
Conclusions: Pre-diagnostic plasma C-reactive protein concentration was not associated with an increased risk of colorectal adenoma. More work is needed to determine whether C-reactive protein is a valid marker of intra-colonic inflammation, and whether such inflammation contributes to the etiology of colorectal neoplasia.