It turns out that soyfoods could actually cut the risk of breast cancer recurrence.
While women diagnosed with breast cancer are often told not to eat soyfoods or soy-based supplements because they can interfere with anti-estrogen treatment, a new animals study, conducted at Georgetown Lombardi Comprehensive Cancer Center, a long history of eating soyfoods boosts the immune response against breast tumors.
Lead investigator of the study, Prof. Leena Hilakivi-Clarke, PhD, said that it was concerning that some patients might just start taking soy supplements when they shouldn't and that others would stop eating soyfoods when they could really benefit from them.
The notion that soy, specifically genistein (an isoflavone), could stimulate the growth of breast cancer cells and disrupt anti-estrogen treatment has been based on studies in mice that didn't have immune cells known as cytotoxic T cells, known to attack breast cancer. This led oncologists to advise their breast cancer patients not to eat soyfoods.
The researchers investigated if their previous findings could be explained by changes in tumor immune responses. While T cells can attack tumor cells, other immune cells can disable the ability of these T cells to recognize that tumors are present, allowing breast cancer to grow unchecked by the immune system.
Hilakivi-Clarke said the findings mirror observational studies that found women who have long been consuming more than 10 mg isoflavones daily are at reduced risk of breast cancer recurrence, compared with women who consume less than 4 mg isoflavones daily. "One cup of soymilk has about 30 mg isoflavones, the majority of which is genistein."
The study was presented at the American Association for Cancer Research (AACR) Annual Meeting 2015.
