A prospective survey evaluating the use of soy products in breast cancer

Abstract

10562 Background: Many studies have evaluated the potential role of soy in the prevention of breast cancer. A number of components in soy appear to have anticancer properties, including isoflavones, genistein and daidzein. The use of soy by women with breast cancer is now being questioned because of the estrogen-like effects of isoflavones and possible interactions with tamoxifen. Clinicians providing nutrition counseling to these women are concerned because the availability of soy foods has increased dramatically in the past few years. The goal of this study was to quantify the intake of isoflavones in women with breast cancer to determine if their intake is of clinical significance. Methods: We evaluated a consecutive case series of 100 women with breast cancer treated at Cancer Treatment Centers of America between 09/03 and 02/04. After obtaining informed consent, each patient was asked to complete a soy food frequency questionnaire (FFQ) that was scored by Fred Hutchinson Cancer Research Center, the institute that developed and validated FFQ. Results: Mean age was 50.5 years (std. dev. = 9.4; range 31–70) and mean BMI was 27.3kg/m2 (std. dev. = 6.75; range 17–59). Table 1 shows detailed characteristics of our patients. Genistein and Daidzein consumption was limited to 65 patients with a mean intake of 81.5 mg/week (std. dev. = 153; range 0.02–682) and 52.9 mg/week (std. dev. = 98.8; range 0.02–482) respectively. Soy foods with highest reported consumption were soy sauce (37%), soy milk (23%), soy bars (18%), roasted soy nuts (13%) and tofu (13%). Conclusions: Our study suggests that the isoflavone intake of breast cancer patients at our hospital was quite variable. Thirty-five patients reported no soy intake. The mean daily intake translates into 11.6 mg genistein and 7.4 mg daidzein, which is equivalent of less than ¼ cup of tofu per day. This amount is slightly higher than what has been previously reported in non-Asian American women. [Table: see text] No significant financial relationships to disclose.