Breast Cancer Patients Who Start Eating Soy After Diagnosis May Trigger Its Return

Breast Cancer Patients Who Start Eating Soy After Diagnosis May Trigger Its Return
Patients who start eating soy products after a breast cancer develops may be at higher risk of cancer recurrence following tamoxifen treatment. But those who already ate soy before a diagnosis may actually be somewhat protected against their cancer coming back after treatment. The study, "Lifetime Genistein Intake Increases the Response of Mammary Tumors to Tamoxifen in Rats," published in Clinical Cancer Research, may help decide a long-standing debate on the benefits and harms of soy consumption in breast cancer patients. The timing of soy's introduction into a person's diet is key, findings suggest. Soybeans contain a compound, genistein, that has a similar structure as estrogen and activates the estrogen receptors. Because estrogen drives the growth of ER-positive breast cancer, which accounts for more than 70 percent of all breast cancer cases, oncologists often advise breast cancer patients not to eat soy products. "Estrogen drives most breast cancer growth, yet high soy intake among women in Asian countries has been linked to a breast cancer rate that is five times lower than Western women, who eat much less soy," the study's senior investigator, Leena Hilakivi-Clarke, PhD, a professor of oncology at Georgetown Lombardi Comprehensive Cancer Center, said in a press release. To understand this apparently contradiction, Hilakivi-Clarke and her team used a breast cancer mouse model to test how different timings of genistein intake could affect breast cancer outcomes. One group of mice was fed a genistein-containing diet right after birth; another group was fed a genistein-based diet only during adulthood. The last group received a genistein diet at the time of tamoxifen treatment, when mammary tumors had already developed. The team found that mi
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