Abstract 3296: Breast mammographic density and the fecal microbiota

Abstract

Abstract The microbial population (microbiota) of the distal human gut has multiple functions that modulate cancer risk including digestion of nutrients, deconjugation and enterohepatic circulation of hormones and other bile acids, and regulation of immunity and inflammation. We have previously reported that postmenopausal breast cancer cases, compared to controls, have lower fecal microbiota alpha diversity, independent of age, body mass index, and estrogen levels, and that the cases’ microbiota is compositionally altered. For deeper understanding of these associations with breast cancer, we compared microbiota metrics to a strong cancer risk factor, breast density, among 48 cancer-free, postmenopausal controls in the Breast and Colon Health study (86% non-Hispanic White, mean age 62 years). In routine screening mammograms, they had the following Breast Imaging Reporting and Data System (BI-RADS, 5th ed.) composition: a) almost entirely fatty (N = 4); b) scattered areas of fibroglandular density (N = 14); c) heterogeneously dense (N = 26); and d) extremely dense (N = 4). As shown in the Table, simple linear regression across these four ordered BI-RADS categories revealed that there was no significant association with fecal microbiota alpha diversity (PD_tree β -0.08, P = 0.56). Breast density in these women also was not associated with microbiota beta diversity (composition) by MiRKAT analysis of un-weighted and weighted UniFrac metrics (P = 0.25 and 0.08, respectively). We conclude that breast density is unlikely to mediate the association of the gut microbiota with breast cancer in postmenopausal women. Fecal alpha diversity by mammographic density categoryBI-RADS DensityNo.Mean (SD) PD_Whole_TreeAlmost Entirely Fatty436.06 (4.22)Scattered Fibroglandular1438.18 (8.25)Heterogeneously Dense2637.19 (4.88)Extremely Dense438.33 (7.99) Citation Format: Gieira S. Jones, Heather S. Feigelson, Jacques Ravel, James J. Goedert. Breast mammographic density and the fecal microbiota. [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 3296.