In a study conducted in rats, researchers at the University of Illinois at Chicago found that tamoxifen alone reduced the number of carcinogen-induced tumors by 29 percent, from an average of 7.9 per rat to 5.6. Similarly, soy alone reduced the number of tumors by 37 percent. But when the two were combined, the overall reduction in number of tumors was 62 percent. The results of the study were reported at the annual meeting of the American Association of Cancer Research in New Orleans on March 28. Constantinou and colleagues are now studying whether the additive effects of soy seen in this animal study are due to compounds known as phytoestrogens or to other components of soy.
Breast cancer is currently the most common cancer in women.
It is estimated that over 800,000 cases and 400,000 deaths occur each year worldwide. The disease has a clear genetic component, such as mutations in the BRCA1 or BRCA2 genes. But on a population basis, the major risks are due to lifestyle and environmental factors, such as poor dietary habits and exposure to carcinogens. Diet is estimated to contribute to up to 50 percent of all newly diagnosed breast cancer cases.