Inflammatory potential of diet in association with breast cancer risk: A matched case-control study

Abstract

Background: The present study aimed to explore the association between the dietary inflammatory index (DII ® ) and the risk of different molecular subtypes of breast cancer (BrCa) for the first time in a large population-based case-control study conducted in Iran.Methods: The subjects consisted of 1007 women with histopathologically confirmed BrCa, and 1004 controls admitted to hospitals in Tabriz, Iran, for non-neoplastic conditions. The DII scores were computed based on dietary intake collected using a validated 136-item food frequency questionnaire. Energy-adjusted DII (E-DII TM ) also were calculated. Conditional logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs).Results: The pro-inflammatory diet [highest E-DII quartile (Q)] vs. the anti-inflammatory diet (lowest E-DII scores) showed significantly increased BrCa risk (OR Q4 vs. Q 1 : 1.87; 95% CI: 1.42‒2.47). This was aligned with the findings obtained in women at reproductive ages (premenopausal status) who diagnosed with luminal A [estrogen receptor-positive (ER + ) and/or progesterone receptor-positive (PR + ) and human epidermal growth factor receptor 2-negative (HER2 - )] (OR Q4 vs. Q 1 : 2.71; 95% CI: 1.74‒4.22) and luminal B (ER + and/or PR + , HER2 + ) (OR Q4 vs. Q 1 : 2.86; 95% CI: 1.39‒5.89). Women in the highest E-DII quartile were three times more likely to have triple-negative BrCa (ER - , PR - , HER2 - ) compared to luminal A (OR Q4 vs. Q1 : 3.00; 95% CI: 1.002‒8.96). Likewise, the risk of HER2-enriched BrCa (ER - , PR - and HER2 + ) vs. luminal B subtype was increased among those consumed the most pro-inflammatory E-DII (OR Q4 vs. Q1 : 2.44; 95% CI: 1.01‒5.88). A significant ascending trend was observed in mean E-DII scores, followed by rising tumor size (P=0.018).Conclusions: The pro-inflammatory diet, as indicated by increasing E-DII scores, was a risk factor of BrCa in Iranian women, providing updates to the invasive molecular subtypes of BrCa. Diets modulated for high anti-inflammatory and low pro-inflammatory dietary components are suggested to prevent the risk of more aggressive forms of BrCa.