Abstract 1738: A pooled analysis of carbohydrate and dietary fiber intake and prostate cancer risk

Abstract Scientific findings on the association between carbohydrate intake (both quantity and quality) and prostate cancer (CaP) risk are conflicting. We examined this association in the Pooling Project of Prospective Studies of Diet and Cancer, a consortium of 15 cohorts with validated measures of dietary intake. During follow-up of 842,149 men, 52,683 were diagnosed with CaP. We examined associations between carbohydrate and fiber intake and 3 different definitions of advanced CaP: 1) Advanced cases were defined as men with tumors that were advanced at diagnosis (T4, N1, and/or M1) or men who died of CaP during follow-up regardless of diagnosed stage (n = 4,934); 2) Advanced (restricted) cases were defined as above, but excluded men diagnosed with localized CaP who later died of Cap (n = 3,091); and 3) Fatal CaP was defined as men who died of CaP (n = 3,097). We performed Cox proportional hazards models to calculate study-specific multivariable relative risks (RR) and pooled these results using random effects models. Models were adjusted for age, race/ethnicity, education, marital status, body mass index, height, smoking status, family history of CaP, physical activity, history of diabetes, multivitamin use, and energy and alcohol intake. Median total carbohydrate intake across studies ranged from 41% - 64% of total energy intake. Preliminary analyses were suggestive of a modest inverse association between carbohydrate intake and risk of advanced and fatal CaP. The pooled multivariable adjusted RR (MVRR) comparing the highest versus lowest study-specific quintile of carbohydrate intake (percent of energy) was 0.90 (95% confidence interval [CI] 0.81-1.01; trend test p-value 0.06) for advanced CaP and 0.91 (0.97-1.04; trend test p-value 0.16) for advanced (restricted) Cap. For fatal CaP, the pooled MVRR for the same comparison was 0.88 (95% CI 0.77-1.00), trend test p-value 0.05. Findings were similar for energy-adjusted total carbohydrates (g/day) or available carbohydrates (total carbohydrates - dietary fiber). When total carbohydrate intake was categorized using common absolute cutpoints across studies, no significant change in risk was observed for men consuming ≥ 60% vs 45%-<50% energy for carbohydrates for advanced, advanced (restricted) or fatal CaP. Total dietary fiber intake was not statistically significantly associated with risk of advanced, advanced (restricted), or fatal CaP; men in the highest versus lowest quintile of intake had nonsignificant 3%-11% lower risks. No statistically significant between-studies heterogeneity was observed for any of these estimates. Although these preliminary findings suggest a modest inverse association for carbohydrate intake and CaP risk, further analyses on carbohydrate quality (glycemic index and load, refined vs whole grains) and examination of the effect of substituting carbohydrates for other macronutrients are needed. Citation Format: Elkhansa Sidahmed, Stephen J. Freedland, Kana Wu, Jeanine M. Genkinger, Stephanie A. Smith-Warner. A pooled analysis of carbohydrate and dietary fiber intake and prostate cancer risk. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1738.