Abstract 3769: Use of combined levels of dietary intake from FFQ and plasma biomarkers to assess association between antioxidant exposures and prostate cancer risk

Abstract

Abstract Epidemiologic studies evaluating the relation between specific nutrients and risk of disease typically rely either on questionnaire-based or on biomarker-based measures of exposure; however both of these approaches may be affected by systematic error. In this study, we aim to improve assessment of antioxidant exposure through a combined measure reflecting both plasma measurements and food frequency questionnaire (FFQ)-derived levels of intake. This combined measure of exposure is examined in relation to risk of prostate cancer. In this community-based case-control study, dietary intake was assessed through the validated Block FFQ that allowed estimating daily intakes of various antioxidants. Archived plasma samples were analyzed using high performance liquid chromatography to determine circulating levels of carotenoids (lycopene, α-carotene, β-carotene, lutine, and β-cryptoxanthin), retinol (vitamin A), and α-tocopherol (vitamin E). Cases and controls were categorized as having “high” or “low” for each antioxidant's dietary intake and plasma level based on the median value among controls. Each participant was then included into one of the following four categories: (1) low dietary intake and low plasma level; (2) low dietary intake and high plasma level; (3) high dietary intake and low plasma level; and (4) high dietary intake and high plasma level. The combined measurements of high dietary intake and high plasma levels of lycopene, β-cryptoxanthin, and α-tocopherol demonstrated a statistically significant association with prostate cancer risk with adjusted odds ratios of 0.46 (0.23-0.91), 0.43 (0.22-0.84), and 0.32 (0.14-0.72), respectively. The combined measurements of high dietary intake and low plasma levels of β-carotene also demonstrated a statistically significant association (aOR = 0.43; 95% CI=0.20-0.91) with prostate cancer risk. These results tended to be stronger than the corresponding results for each measure of exposure considered individually. These findings provide evidence that the use of combined levels of dietary intake from FFQ and plasma biomarkers can improve the assessment of antioxidant exposure compared to use of either FFQ or plasma biomarkers separately. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3769.