Diet/Drug Interactions – A collaboration between NCTR (National Center For Toxicological Research) and the University of Southern California has shown that circulating levels of tamoxifen and its therapeutically active metabolites in Asian women (n=380) undergoing therapy for breast cancer was not affected by dietary soy intake. By comparison, this study also showed that age/menopausal status, body weight, and use of hypertensive medications, particularly diuretics, significantly influenced the circulating levels of tamoxifen and its metabolites.
However, approximately one-third of patients with estrogen-receptor positive tumors do not ever respond to tamoxifen therapy, and patients eventually can become resistant to the therapeutic benefits of tamoxifen treatment. Future studies that include breast cancer survival and relapse assessments will be needed to determine whether soy isoflavones can affect the overall efficacy of tamoxifen chemotherapy.
These findings recently were published by Wu et al. in Journal of Clinical Oncology published 2007; Vol 25; 3024-3030. For further information, contact Dr. Tom Flammang or Dr. Dan Doerge at NCTR.
tag: breast cancer, NCTR, tamoxifen, dietary soy, Clinical Oncology