Phytoestrogens and indicators of breast cancer prognosis

Breast cancer incidence is lower and survival is longer in Asian women residing in Japan, China, or the Philippines than Caucasian women residing in the United States. Phytoestrogen intake has been examined as a possible reason for the disparity in breast cancer incidence and survival. This study examined the association between phytoestrogen intake prior to diagnosis of breast cancer and indicators of breast cancer prognosis (tumor size, estrogen and progesterone receptor status, histological grade, lymphovascular invasion, nodal spread, and stage) in 128 women, aged 40-79 yr, newly diagnosed with invasive breast cancer. After controlling for significant confounding factors, higher intakes of phytoestrogens were associated with favorable indicators of breast cancer. In women with higher intakes of phytoestrogens, there was a 32% reduction in the odds of being diagnosed with any stage of cancer other than stage 1 (95% confidence interval, CI = 0.49-0.93; P = 0.02), a 38% reduction in odds of being diagnosed with positive lymphovascular invasion (95% CI = 0.40-0.95; P = 0.03), and a 66% increase in the odds of being diagnosed with a positive progesterone receptor (95% CI = 1.06-2.58; P = 0.03). We conclude that phytoestrogen intake prior to diagnosis may improve prognosis of breast cancer.