Association Between Post-Cancer Diagnosis Dietary Inflammatory Potential and Survival in WHI Observational Study and Dietary Modification Trial

Background: Inflammation regulates key biologic processes in chronic disease and can be modulated by diet. Our objective was to use the dietary inflammatory index (DII), a novel tool to characterize the inflammatory potential of diet, to examine how post-cancer diagnosis dietary quality is associated with overall survival in the Women's Health Initiative (WHI) Observational Study (OS) and Dietary Modification Trial (DM). Methods: After excluding baseline cancers and energy outliers, the analytical cohort had 4,241 postmenopausal women (19% of total cancer cases), aged 50 to 79 years at baseline, in the WHI OS (n = 1,852) and DM (n = 2,389), who developed invasive cancer during follow-up and completed a food frequency questionnaire after diagnosis. These women were followed from dietary assessment until death from any cause. Energy-adjusted DII scores from food only and from food plus supplement (any reported dietary supplement related to DII parameters) after cancer diagnosis for each subject were calculated by multiplying the inflammatory effect scores determined based on extensive literature review and intake values for each food parameter, and then summing across all the food parameters. Death was ascertained by clinical center follow-up or by searching the National Death Index with central or local adjudication. Cox proportional hazards models were fit to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CI) for all-cause mortality comparing women in higher DII quartiles with those in the first quartile. Results: After a median 11.2 years of follow-up, 1,470 deaths occurred. After adjustment for key covariates, women who consumed a more pro-inflammatory diet (in higher quartiles of DII score from food only) after a cancer diagnosis had a significantly higher risk of death from any cause compared to women consuming a more anti- inflammatory diet (HR Q4:Q1 = 1.18; 95% CI, 1.01–1.38; P trend = 0.015). In analyses using DII score from both diet and supplements, a pro-inflammatory DII score was associated with even higher risk of all-cause mortality (HRQ4:Q1 = 1.63; 95% CI, 1.40–1.91; P trend < 0.0001). Conclusions: Consuming a more pro-inflammatory diet after cancer diagnosis was associated with increased risk of death from any cause.