Thompson LU, Li T, Chen J, Goss PE Nutritional Sciences, University of Toronto, Toronto, ON, Canada; Medical Oncology, Princess Margaret Hospital, Toronto, ON, Canada Epidemiological studies and biological properties of mammalian lignans derived from plant precursors (phytoestrogens) suggest that they may have anticancer potential. Flaxseed, the richest source of mammalian lignan precursors, has previously been shown to reduce the mammary tumor number and growth of established tumors in rats. The aim of this study was to examine, in a randomized double blind, placebo controlled, prospective clinical trial, the effects of dietary flaxseed on tumor biology, urinary lignan excretion and side effects in patients with newly diagnosed breast tumors. Patients were randomized to either a 25g flaxseed containing muffin (6 pre-, 17 post-menopausal) or a control (placebo) muffin (4 pre-, 12 post-menopausal). At initial diagnostic core biopsy and at definitive surgery, (a) tissues were analyzed for rate of tumor cell proliferation(Ki67 labeling index and score), c-erB-2 expression, and estrogen (ER) and progesterone (PR) receptor levels, (b) 24-hr urine samples were collected and analyzed for lignans, and (c) 3-day diet records were analyzed for nutrient intake. Side effects were monitored. Mean treatment times were 39 and 38 days in the placebo and flaxseed groups, respectively. In postmenopausal women, significant reductions (21-33%) in Ki67 labeling index (p<.036) and scores (p<.029) and in the c-erB-2 expression (p<.040) were observed in the flaxseed group but not in the placebo group. These changes are comparable to those seen with tamoxifen using similar study protocol. No significant differences in the ER and PR levels and in caloric and macronutrient intakes were seen between groups and between pre- and post- treatment periods. Significantly higher post-treatment urinary lignan excretion was observed in the flaxseed group compared with placebo and with pre-treatment levels. No significant adverse effects of flaxseed were reported. This study showed, for the first time, the potential of dietary modification with flaxseed and its components such as the lignans, in reducing tumor growth in patients with breast cancer comparable to the effects seen with preoperative tamoxifen. Ann's NOTE: This study generated a lot of excitement. Too bad the STAR trial comparing Tamoxifen to Raloxifene did not include an arm for flaxseed and other dietary interventions. Also note that the researchers were able to measure the results and did NOT depend on subjective response (not that subjective response is bad). San Antonio Breast Cancer Symposium 2000 |
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