Key Findings
Flaxseed lignans are diphenolic compounds structurally similar to endogenous estrogens and synthetic Tamoxifen. The major circulating lignan, enterolactone, is a weak estrogen compared to estradiol. Lignans have been shown to work synergistically with Tamoxifen to reduce breast tumor growth. This randomized intervention study between tumor biopsy and resection, in postmenopausal women diagnosed with estrogen receptor positive (ER plus) breast cancer, assessed the effect of ground flaxseed compared to the drug, the aromatase inhibitor (AI), anastrozole. No effect of flaxseed on AI activity related to breast tumor characteristics, growth hormone, or serum steroid hormone levels, although the sample size may have been too small to find effects. Results suggest that AI therapy might reduce the production of circulating mammalian lignans from flaxseed.
ABSTRACT
Use of complementary approaches is common among breast cancer survivors. Potential interactions between aromatase inhibitors (AI) and high phytoestrogen foods, such as flaxseed (FS), are not often described. We conducted a pilot 2 by 2 factorial, randomized intervention study between tumor biopsy and resection, in 24 postmenopausal women with estrogen receptor positive (ER plus) breast cancer, to assess the effects of FS and anastrozole, and possible interactions between them, on serum steroid hormone and tumor related characteristics associated with long term survival. The effect of each treatment vs. placebo on outcomes was determined by linear regression adjusting for pretreatment measure, stage, and grade. Although not statistically significant, mean ER beta expression was approximately 40 per cent lower from pre to post intervention in the FS plus AI group only. We observed a statistically significant negative association for androstenedione in the FS plus AI group vs. placebo and for DHEA with AI treatment. Enterolactone excretion was much lower in the FS plus AI group compared to the FS group. Our results do not support strong effects of FS on AI activity for selected breast tumor characteristics or serum steroid hormone levels but suggest AI therapy might reduce the production of circulating mammalian lignans from FS. (Authors abstract)
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