Lilian U Thompson, Jian Min Chen, Tong Li, Kathrin Strasser-Weippl, Paul E Goss
Journal: Clinical cancer research : an official journal of the American Association for Cancer Research 2005;11(10):3828-35
PMID: 15897583
High levels of the hormone oestrogen are linked with an increased risk of developing breast cancer. Plant lignans have similar chemical structures to oestrogen and may block the action of oestrogen in breast cancer cells. Flaxseed (also known as linseed) is a rich source of lignan precursors and has been shown to reduce tumour growth in rats. Therefore, it is thought that flaxseed might be effective in cancer treatment and prevention. This randomised, double-blind, placebo-controlled trial examined the effects of dietary flaxseed on tumour growth in postmenopausal women with newly diagnosed breast cancer. Patients were given either a muffin containing 25g of flaxseed or a control muffin, every day from the time of the initial biopsy until undergoing surgery to remove the tumours. They continued to eat their normal diet. The group that ate the flaxseed muffins experienced significant reductions of between 34 and 71% in various markers of tumour growth, and a significant increase in apoptosis of 30%. The control group did not experience any significant changes in these markers. The authors concluded that eating flaxseed has the potential to reduce tumour growth in patients with breast cancer.
PURPOSE
Flaxseed, the richest source of mammalian lignan precursors, has previously been shown to reduce the growth of tumors in rats. This study examined, in a randomized double-blind placebo-controlled clinical trial, the effects of dietary flaxseed on tumor biological markers and urinary lignan excretion in postmenopausal patients with newly diagnosed breast cancer.
EXPERIMENTAL DESIGN
Patients were randomized to daily intake of either a 25 g flaxseed-containing muffin (n = 19) or a control (placebo) muffin (n = 13). At the time of diagnosis and again at definitive surgery, tumor tissue was analyzed for the rate of tumor cell proliferation (Ki-67 labeling index, primary end point), apoptosis, c-erbB2 expression, and estrogen and progesterone receptor levels. Twenty-four-hour urine samples were analyzed for lignans, and 3-day diet records were evaluated for macronutrient and caloric intake. Mean treatment times were 39 and 32 days in the placebo and flaxseed groups, respectively.
RESULTS
Reductions in Ki-67 labeling index (34.2%; P = 0.001) and in c-erbB2 expression (71.0%; P = 0.003) and an increase in apoptosis (30.7%; P = 0.007) were observed in the flaxseed, but not in the placebo group. No significant differences in caloric and macronutrient intake were seen between groups and between pre- and posttreatment periods. A significant increase in mean urinary lignan excretion was observed in the flaxseed group (1,300%; P < 0.01) compared with placebo controls. The total intake of flaxseed was correlated with changes in c-erbB2 score (r = -0.373; P = 0.036) and apoptotic index (r = 0.495; P < 0.004).
CONCLUSION
Dietary flaxseed has the potential to reduce tumor growth in patients with breast cancer.
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