Abstract 5314: Long-term folate intake and prostate cancer risk in the health professionals follow-up study

Abstract

Abstract Background: Randomized trials of supplemental folate and observational studies of circulating folate support a positive association with prostate cancer risk. However, epidemiological studies of dietary and synthetic folate intake are conflicting. Given mandatory folic acid fortification of grains in the US beginning in 1998, evaluation of long-term folate intake from natural and synthetic sources in relation to prostate cancer risk is warranted. Methods: We examined the association between folate intake and prostate cancer risk among 47,884 men in the Health Professionals Follow-up Study who were free from diagnosed cancer at baseline in 1986. Total, natural (from food sources), and synthetic (from supplements/fortification) folate intake was assessed every 4 years using a validated food frequency questionnaire, and categorized as the cumulative average and lagged (0-4, 4-8, 8-12, and 12-16 years in the past) intakes. Cox proportional hazards regression was used to calculate multivariable hazard ratios (HRs) and 95% confidence intervals (CI). Results: We identified 6,186 incident prostate cancer cases from 1986-2012, including 1,078 with lethal disease (distant metastasis or death). Mean total folate intake was 481 µg/day in 1986 and increased to 671 µg/day by 2010. The proportion of men meeting the recommended intake of 400 µg/day increased from 47% in 1986 to 74% after fortification began in 1998. Folate intake was positively correlated with physical activity, multivitamin use, and PSA testing, and inversely correlated with smoking. Total folate intake averaged over time was not significantly associated with total prostate cancer risk: HR≥800 vs. 400-599=1.03 (95% CI: 0.95-1.13, p-trend=0.76). Neither natural nor synthetic folate intake was associated with risk of total prostate cancer. No associations were observed between total, natural, or synthetic folate intake and risk of lethal, advanced stage, or high-grade disease. Conclusions: Our findings do not support strong associations between intakes of total, natural, or synthetic folate and prostate cancer risk. We found no indication that folate intake of ≥800 µg/day (twice the recommended level) increases prostate cancer risk. Citation Format: Nadine M. Hamieh, Julie L. Batista, Sarah C. Markt, Mary K. Downer, Lorelei A. Mucci, Meir J. Stampfer, Edward L. Giovannucci, Kathryn M. Wilson. Long-term folate intake and prostate cancer risk in the health professionals follow-up study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5314. doi:10.1158/1538-7445.AM2017-5314