Context Inflammation may play a role in the pathogenesis of colorectal cancer;
however, epidemiological evidence supporting this hypothesis in average-risk
persons is sparse.
Objective To determine the risk of incident colon and rectal cancer associated
with elevated baseline plasma concentrations of C-reactive protein (CRP).
Design, Setting, and Participants Prospective, nested case-control study of a cohort of 22 887 adults
(>18 years and Washington County, Maryland, residents) enrolled between May
and October 1989 and followed up through December 2000. A total of 172 colorectal
cancer cases were identified through linkage with the Washington County and
Maryland State Cancer registries. Up to 2 controls (n = 342) were selected
from the cohort for each case and matched by age, sex, race, and date of blood
Main Outcome Measure Odds ratio (OR) of incident colon and rectal cancer.
Results Plasma CRP concentrations were higher among all colorectal cases combined
than controls (median CRP, 2.44 vs 1.94 mg/L; P =
.01). The highest concentration was found in persons who subsequently developed
colon cancer vs matched controls (median CRP, 2.69 vs 1.97 mg/L; P<.001). Among rectal cancer cases, CRP concentrations were not
significantly different from controls (median CRP, 1.79 vs 1.81 mg/L; P = .32). The risk of colon cancer was higher in persons
in the highest vs lowest quartile of CRP (OR, 2.55; 95% confidence interval
[CI], 1.34-4.88; P for trend = .002). In nonsmokers,
the corresponding association was stronger (OR, 3.51; 95% CI, 1.64-7.51; P for trend<.001). A 1-SD increase in log CRP (1.02
mg/L) was associated with an increased risk of colon cancer after adjusting
for potential confounders and excluding cases occurring within 2 years of
baseline (OR, 1.35; 95% CI, 1.05-1.74) or excluding those with late-stage
colon cancer at the time of diagnosis (OR, 1.38; 95% CI, 0.99-1.91).
Conclusions Plasma CRP concentrations are elevated among persons who subsequently
develop colon cancer. These data support the hypothesis that inflammation
is a risk factor for the development of colon cancer in average-risk individuals.