Researchers thought that only hormone-responsive breast cancers would be affected by breast-feeding.

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The FDA approved the new treatment for about 20 percent of breast cancer patients with a form of the disease that is typically more aggressive and less responsive to hormone therapy.

NPR: FDA Approves New Targeted Breast Cancer Drug

The animals also became more responsive to the hormone insulin, which controls the way the body uses sugar.

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Other treatments include hormone therapy if the cancer is responsive to estrogen.

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