Background: Observations that risk for colorectal cancer is elevated in patien ts with inflammatory bowel disease and that long-term use of anti-inflammatory drugs may reduce colorectal cancer risk have raised the possibility that inflam mation may play a role in the development of colorectal cancer. While a recent p rospective study observed a positive association between C-reactive protein(CRP ), a marker of inflammation, and risk for colon cancer, data testing this hypoth esis are sparse. Objective:To evaluate whether plasma CRP levels predict colorec tal cancer risk in women. Design: Prospective cohort study, with 97%morbidity f ollow-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 ol der 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: S elf-reported incident colorectal adenocarcinoma confirmed by medical record rev iew. Results: 169 women de- veloped colorectal adenocarcinomas during follow-up. Baseline CRP levels were not significantly associated with colorectal cancer risk. The multivariate haza rd ratios according to cutoff points for CRP proposed in clinical guidelines wer e 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 compa red with the category of less than 1 mg/L. High CRP levels were also not associa ted with increased risk in analyses done according to tumor location and stage a t diagnosis,according to alternative cutoff points for CRP, or in any of the sub groups evaluated. Limitations: Despite multivariate analysis, residual confoundi ng might still be present. Although this study was prospective, we cannot comple tely exclude undetected cancer at baseline.Measur- ements for CRP were available for only 71%of women in the cohort; however, th e women who did and those who did not provide blood were mostly similar. Conclus ions: Plasma CRP levels do not appear to predict an increased risk for developin g colorectal cancer in apparently healthy women. Low-grade inflammation may not play an important role in increasing the risk for colorectal cancer.
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