Repeated measurements of serum carotenoid, retinol and tocopherol levels in relation to colorectal cancer risk in the Women's Health Initiative
Menée auprès de 5 477 femmes de la cohorte "Women's Health Initiative", cette étude évalue l'association entre les niveaux sériques de caroténoïdes, de rétinol et de tocophérol, mesurés à intervalles réguliers, et le risque de cancer colorectal
Background/Objective:Previous cohort studies examining the association of serum antioxidant levels and risk of colorectal cancer have used a single (baseline) measurement only. In the present study, we assessed the association of serum levels of eight antioxidant nutrients in relation to risk of colorectal cancer, using repeated measurements.Subjects/Methods:Data on a subsample of women in the Women's Health Initiative with repeated measurements of serum retinol, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein+zeaxanthin, lycopene, alpha-tocopherol and gamma-tocopherol during follow-up were included in the analysis. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CIs).Results:Among 5477 women with baseline serum antioxidant values, 88 incident cases of colorectal cancer were identified over a median follow-up time of 12 years. Serum antioxidants measured at baseline generally showed no association with risk of colorectal cancer, although serum beta-carotene at baseline showed a non-significant inverse association with colon cancer alone. Furthermore, using the repeated measurements of beta-carotene, the average of all measurements was inversely associated with risk of both colorectal and colon cancer: HRs for highest vs lowest tertile 0.54, 95% CI 0.31-0.96, and 0.47, 95% CI 0.25-0.88, respectively. No associations were seen with other antioxidant nutrients in the repeated measure analyses.Conclusions:In this study, baseline levels of antioxidant nutrients were not associated with risk of colorectal or colon cancer; however, using repeated measures, a relatively high serum level of beta-carotene (average of all measurements) was inversely associated with risk of colon and colorectal cancer in postmenopausal women.European Journal of Clinical Nutrition advance online publication, 14 December 2011; doi:10.1038/ejcn.2011.207.