Abstract 5255: A pooled analysis of dietary fiber intake and risk of prostate cancer
Authors: Sidahmed Elkhansa , Freedland Stephen J. , Wang Molin , Wu Kana , Genkinger Jeanine M. , Smith-Warner Stephanie A. 
Published: August 2018

Abstract
High dietary fiber intake has been associated with a lower risk of many cancers but evidence from epidemiological studies on dietary fiber intake and risk of advanced prostate cancer and prostate cancer mortality are limited. We examined associations between dietary fiber intakes overall and from grains, fruits, and vegetables and risk of prostate cancer in 15 cohorts in the Pooling Project of Prospective Studies of Diet and Cancer. Among 842,149 men, during maximum follow-up ranging from 9.2-21.9 years across studies, 52,683 incident prostate cancer cases were identified. Prostate cancer outcomes examined were: 1) all cases; 2) advanced cases, which included men with advanced stage prostate cancer at diagnosis (T4, N1, and/or M1) and men who died of prostate cancer during follow-up (n=4,924); 3) advanced (restricted) cases, which included only men with advanced stage prostate cancer at diagnosis (n=3,110) (men diagnosed with localized prostate cancer who died of prostate cancer were excluded) and 4) prostate cancer mortality, death due to prostate cancer (n=3,199). We adjusted dietary fiber intake for energy intake using the residual method. Cox proportional hazards models were used to calculate study-specific multivariable relative risks (MVRR); the study-specific results were pooled using random effects models. Models were adjusted for age, race/ethnicity, education, marital status, body mass index, height, smoking status, family history of prostate cancer, physical activity, history of diabetes, multivitamin use, and energy and alcohol intake. Median dietary fiber intake varied from 6-28 g/d across studies. For total dietary fiber intake, dietary fiber intake from fruits, and dietary fiber intake from vegetables, no statistically significant associations were observed for any outcome; the pooled MVRRs comparing the highest with the lowest quintile ranged from 0.95-1.02. The pooled MVRR comparing the highest with the lowest study-specific quintile of dietary fiber intake from grains was 0.84 (95% confidence interval [CI] 0.76-0.93) for advanced stage and 0.85 (0.74-0.97) for advanced (restricted) stage prostate cancer. The pooled MVRR for the same comparison was 0.78 (95% CI 0.69-0.89) for prostate cancer mortality. Similar results were observed when dietary fiber intake was categorized using common absolute intake cutpoints across studies (e.g., the pooled MVRR for prostate cancer mortality was 0.86, 95% CI 0.75-0.98 comparing ≥8 with &lt;2 g/d of dietary fiber intake from grains). Further adjustment for dietary folate, calcium, and lycopene intake and red meat consumption did not substantially change the results for dietary fiber intake from grains. In this large, international consortium, we found that higher dietary fiber intake from grains, but not intake of dietary fiber overall or from fruits and vegetables, was associated with lower risk of advanced prostate cancer and prostate cancer mortality.
Citation Format: Elkhansa Sidahmed, Stephen J. Freedland, Molin Wang, Kana Wu, Jeanine M. Genkinger, Stephanie A. Smith-Warner. A pooled analysis of dietary fiber intake and risk of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5255.