Dietary lignan intake and the clinical characteristics of breast cancer

Dietary phytoestrogens have been studied as potentially etiologic factors of female breast cancer due to their bioactivity as estrogen receptor agonists/antagonists and their demonstrated anticancer properties. Dietary lignans, a type of phytoestrogen found primarily in plant foods such as whole grains and berries, have been linked to decreased risk of breast cancer and specific tumor characteristics including estrogen and progesterone receptor negativity. Lignan intake may modulate the manifestation of breast cancer through its relationship with prognostically relevant tumor characteristics. We investigated the relationships between dietary intake of total lignans and specific lignans, matairesinol, lariciresinol, pinoresinol, and secoisolariciresinol, and breast cancer tumor characteristics in 683 women with incident, histologically-confirmed breast cancer enrolled in the Data Bank and Biorepository (DBBR) at Roswell Park Cancer Institute. Data extracted from medical records included the cancer tumor characteristics, hormone receptor status [+/- for estrogen (ER), progesterone (PR), human epidermal growth factor 2 (HER2)], tumor stage, grade, and tumor subtype (Luminal A, Luminal B, HER2+/ER-, ER-/PR-/HER2-). Dietary lignan exposure was quantified from completed DBBR food frequency questionnaires and food composition information. Statistical evaluation of the relationships between lignan intake and the tumor characteristics was stratified by menopausal status (247 premenopausal, 436 postmenopausal women). No statistically significant relationship was observed between intake of total or specific dietary lignans and breast cancer tumor characteristics in premenopausal women. Among postmenopausal women the data suggest there is a relationship between higher lignan intake and ER-negativity (p=0.052) and PR-negativity (p=0.037), although the results were statistically insignificant after adjustment for potential confounders (ER: p=0.068, PR: p=.136). Our results support future study of dietary lignan intake and breast cancer clinicopathologic characteristics in pre- and postmenopausal women separately due to the different relationships observed in these women with differing hormonal milieu. Lignan intake was associated with ER- and PR-negative breast cancer tumors in postmenopausal women only, although more research with larger groups of premenopausal women, more precise assessment of lignan intake, and complete clinical data are needed to further describe the relationship between dietary lignans and breast cancer tumor characteristics.