C-reactive protein levels are not associated with increased risk for colorectal cancer in women

Background: Observations that risk for colorectal cancer is elevated in patients with inflammatory bowel disease and that longterm use of anti-inflammatory drugs may reduce colorectal cancer risk have raised the possibility that inflammation may play a role in the development of colorectal cancer. While a recent prospective study observed a positive association between C-reactive protein (CRP), a marker of inflammation, and risk for colon cancer, data testing this hypothesis are sparse. Objective: To evaluate whether plasma CRP levels predict colorectal cancer risk in women. Design: Prospective cohort study, with 97% morbidity follow-up and 100% mortality follow-up within the past 2 years. Setting: women's Health Study. Participants: 27 913 apparently healthy women age 45 years or older who had CRP measured at entry into a trial of low-dose aspirin and vitamin E. Maximum length of intervention and follow-up was 10.8 years. Measurements: self-reported incident colorectal adenocarcinoma confirmed by medical record review. Results: 169 women developed colorectal adenocarcinomas during follow-up. Baseline CRP levels were not significantly associated with colorectal cancer risk. The multivariate hazard ratios according to cutoff points for CRP proposed in clinical guidelines were 0.79 (95% CI, 0.53 to 1.17) for the category of 1 to 3 mg/L and 0.66 (CI, 0.43 to 1.03) for the category of greater than 3 mg/L (P for trend = 0.09), as compared with the category of less than 1 mg/L. High CRP levels were also not associated with increased risk in analyses done according to tumor location and stage at diagnosis, according to alternative cutoff points for CRP, or in any of the subgroups evaluated. Limitations: Despite multivariate analysis, residual confounding might still be present. Although this study was prospective, we cannot completely exclude undetected cancer at baseline. Measurements for CRP were available for only 71% of women in the cohort; however, the women who did and those who did not provide blood were mostly similar. Conclusions: Plasma CRP levels do not appear to predict an increased risk for developing colorectal cancer in apparently healthy women. Low-grade inflammation may not play an important role in increasing the risk for colorectal cancer.