In vitro and in vivo studies have associated
iron with both the initiation and promotional stages of
carcinogenesis. We investigated whether
iron was associated with
colorectal cancer in a nested case-control study within the
alpha-tocopherol,
beta-carotene cancer prevention study cohort. Exposure was assessed at baseline, using a 276-item food frequency questionnaire and a fasting serum sample. The study included 130
colorectal cancer cases (73
colon cancers and 57
rectal cancers) and 260 controls. Conditional logistic regression was used to estimate odds ratios (
ORs) and 95% confidence intervals (CIs). Supplemental
iron intake was only reported for 4 cases and 18 controls; therefore, we were unable to obtain meaningful results for this variable. Comparing the highest to the lowest quartiles, there was an inverse association between serum
ferritin and
colorectal cancer risk (OR = 0.4, 95% CI = 0.2-0.9) and a suggestion of an inverse association between
dietary iron and
colorectal cancer risk (OR = 0.4, 95% CI = 0.1-1.1). In addition, serum
ferritin, serum
iron and
transferrin saturation were all inversely associated with
colon cancer risk specifically (OR = 0.2, 95% CI = 0.1-0.7, p trend = 0.02; OR = 0.2, 95% CI = 0.1-0.9, p trend = 0.05; OR = 0.1, 95% CI = 0.02-0.5, p trend = 0.003, respectively), whereas serum unsaturated
iron binding capacity was positively associated with
colon cancer risk (OR = 4.7, 95% CI = 1.4-15.1, p trend = 0.009). In summary, we found a significant inverse association between several serum
iron indices and
colon cancer risk.