Dietary Patterns and Risk of Invasive Ductal and Lobular Breast Carcinomas: A Systematic Review and Meta-analysis.

The histopathologic subtypes of breast cancer, including invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC), differ in terms of risk factors, progression, and response to treatment. The PubMed/Medline, Web of Science, and Scopus databases were searched up to February 2020 for published studies on the association between dietary patterns (Western diet [WD] or Mediterranean diet [WD]) and the risk of IDC/ILC of breast. Multivariable adjusted relative risk (RR) and 95% confidence intervals (CIs) comparing the highest and lowest categories of WD and MD patterns were combined by using the random-effects meta-analyses. After searching the databases, 10 eligible studies on the association of diet and IDC (7 articles) and ILC (3 articles) were included in the analysis. A statistically significant adverse association was observed between MD and IDC in case-control studies (RR = 0.47; 95% CI, 0.39-0.55; I = 85.1%; P < .001). However, the association was nonsignificant in cohort studies (RR = 0.98; 95% CI, 0.92-1.05; I = 88.8%; P = .003). The pooled analysis also suggested a significant and direct association between the WD and the risk of IDC (RR = 1.36; 95% CI, 1.18-1.53; I = 63.7%; P = .017). The risk of ILC for the highest compared to the lowest category of MD was highly protective (RR = 0.76; 95% CI, 0.64-0.87; I = 89.2%; P < .001), and a marginally significant association was found between the WD and risk of ILC (RR = 1.45; 95% CI, 1.04-1.86), with no heterogeneity (I = 0; P = .52). This meta-analysis provides supporting evidence for the association between MD decreased risk of IDC and ILC of the breast and the association between WD and increased risk of IDC and ILC. Further investigations are needed to better understand the reasons behind the etiologic mechanisms of how dietary patterns affect patients differently by common breast cancer subtypes, including IDC and ILC.