Abstract 106: Plasma folate and colorectal cancer risk in the Shanghai Men's Health Study.
Authors: Takata Yumie , Shrubsole Martha J. , Li Honglan , Cai Qiuyin , Gao Jing , Wagner Conrad , Zheng Wei , Xiang Yong-Bing , Shu Xiao-Ou 
Published: August 2014

Abstract
Previous epidemiological studies that investigated the association of circulating folate concentration with colorectal cancer risk have generated mixed results. We prospectively evaluated the association of plasma folate concentration with colorectal cancer risk in a case-control study nested within the Shanghai Men's Health Study, a population-based cohort study of 61,483 Chinese men aged 40-74 years at enrollment in the years between 2002 and 2006. Included in the analysis are 289 cases who were diagnosed with incident colorectal cancer through November 2010 and 578 controls who were individually matched to cases on baseline characteristics at the time of plasma sample collection (i.e., age, date, time of day, recent use of antibiotics, time since last meal, and collection of urine sample). Folate concentration in plasma samples was measured by microbiological assay and categorized into tertiles based on the distribution among controls. Conditional logistic regression was used to assess the association between plasma folate and colorectal cancer risk, while adjusting for smoking status, body mass index, multivitamin supplement use, and plasma C-reactive protein (CRP) concentration. Joint associations of plasma folate (tertiles) and CRP, smoking status, alcohol consumption, or time from blood collection to diagnosis with colorectal cancer risk were investigated. The median plasma folate concentrations among cases and controls were 6.87 and 6.81 ng/mL, respectively. A borderline significantly increased risk of colorectal cancer was observed for the middle tertile [odds ratio (OR) = 1.47 and 95% confidence intervals (CI) = 1.00-2.14], but not in the highest (OR = 1.28 and 95% CI = 0.85-1.93), compared with the lowest tertile of plasma folate. This association reached statistical significance for cases diagnosed within 4 years after blood collection (OR = 1.87 and 95% CI = 1.12-3.11). In joint association analysis of folate and CRP level, colorectal cancer risk was significantly elevated (OR = 2.03 and 95% CI = 1.13-3.66) in subjects with the highest tertile of folate and high CRP comparing to those with the lowest tertile of folate and low CRP. These results suggest that in our study population where folate fortification of the food supply and supplement use are uncommon, plasma folate may have a non-linear association with colorectal cancer risk; moderate level of plasma folate (the range: 5.59 to 8.50 ng/mL) may be related to increased colorectal cancer risk, particularly among individuals who are likely to have precancerous changes. Further investigations are needed to elucidate our findings.
Citation Format: Yumie Takata, Martha J. Shrubsole, Honglan Li, Qiuyin Cai, Jing Gao, Conrad Wagner, Wei Zheng, Yong-Bing Xiang, Xiao-Ou Shu. Plasma folate and colorectal cancer risk in the Shanghai Men's Health Study. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 106. doi:10.1158/1538-7445.AM2013-106