In hormone-sensitive breast cancer, estrogen and progesterone fuel tumor growth, which doctors block or inhibit with anti-hormone drugs. Soy isoflavones act like estrogen and, with more women eating soy, researchers wanted to analyze any effect on cancer outcomes.
Scientists measured the diets of 524 women, aged 29 to 72, about half of whom were premenopausal, half postmenopausal. The women had undergone surgery for this type of breast cancer, and were receiving anti-hormone therapy. Cancer was 13 percent less likely to recur in women who consumed the most soy isoflavones.