The association between the inflammatory potential of diet and the risk of histopathological and molecular subtypes of breast cancer in northwestern Iran: Results from the Breast Cancer Risk and Lifestyle study

Abstract

Background: This study explored the association between diet-associated inflammation and the risk of different molecular subtypes of breast cancer (BrCA) in a large, population-based case-control study conducted in northwestern Iran.

Methods: The study consisted of 1007 women with histopathologically confirmed BrCA and 1004 controls admitted to hospitals in Tabriz, northwestern Iran, for nonneoplastic conditions. Dietary Inflammatory Index scores and energy-adjusted Dietary Inflammatory Index (E-DII) scores, with and without supplements, were computed on the basis of dietary intake collected using a validated 136-item food frequency questionnaire.

Results: Women with the highest E-DII scores (quartile 4) versus those with the lowest E-DII scores (quartile 1) showed a significantly increased BrCA risk (odds ratio for quartile 4 vs quartile 1 [OR_Q4vsQ1 ], 1.87; 95% confidence interval [CI], 1.42-2.47), particularly for lobular carcinoma (OR_Q4vsQ1 , 3.07; 95% CI, 1.34-7.02). Findings were similar for premenopausal women diagnosed with luminal A BrCA (OR_Q4vsQ1 , 2.71; 95% CI, 1.74-4.22) or luminal B BrCA (OR_Q4vsQ1 , 2.86; 95% CI, 1.39-5.89). Women consuming the most proinflammatory diets were 3 times more likely to have triple-negative BrCA (OR_Q4vsQ1 , 3.00; 95% CI, 1.002-8.96) while compared to luminal A BrCA. The BrCA risk for women consuming diets in the highest half of E-DII scores (E-DII > 0) was 59% greater than the risk for those in the lowest half (95% CI, 1.29-1.97). Also, higher E-DII scores that took into account supplements were associated with larger tumor sizes (T3 > 5 cm; P < .05).

Conclusions: A proinflammatory diet, as indicated by higher E-DII scores, appears to increase the risk of BrCA in Iranian women. Large increases in risk were seen in invasive molecular subtypes of BrCA. Anti-inflammatory diets are suggested to prevent the risk of overall BrCA and more aggressive forms of BrCA in particular.

Keywords: Dietary Inflammatory Index; breast cancer; hormone receptors; luminal phenotype; molecular subtypes; pathological subtypes; triple-negative.