Dietary intake of phytoestrogens and estrogen receptor status in premenopausal breast cancer patients

While diet may influence estrogen receptor (ER) status, no study has investigated the effect of phytoestrogen intake on this breast cancer prognostic factor. This case-case study examined ER status and usual pre-diagnostic phytoestrogen consumption of 93 premenopausal breast cancer patients. Data were collected from a 207-item food frequency questionnaire and abstracted from medical records. ER-status groups were similar in demographic and anthropometric characteristics, oral contraceptive use, and caloric intake. In univariate analyses, a low intake of genistein, the most potent isoflavone, was associated with increased risk of ER-negative compared to ER-positive breast cancer [odds ratio (OR) = 1.76, 95% confidence interval (CI) = 0.73 − 4.25], while the relationship was weaker for total isoflavones (OR = 1.03, 95% CI = 0.43 − 2.46). Low total phytosterol intake was associated with decreased risk of ER-negative cancer (OR = 0.57, 95% CI = 0.24 − 1.37). These findings suggest that phytoestrogens may influence ER status.