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These drugs are aromatase inhibitors that reduce circulating estrogen. Aromatase is an enzyme complex involving cytochrome P450, which mediates the conversion of androgens to estrogens. Following menopause, aromatization increases in extragonadal sites, such as fat and muscle, and becomes the main source of estrogens. Breast cancer that is driven by estrogen expresses aromatase activity. This is particularly true once tamoxifen resistance has occurred and the cancer that was previously driven by estrogen is now able to convert androgens into estrogens to aid in further proliferation of the cancer. This is more often the case in postmenopausal women. It is this unique ability to inhibit estrogen circulation that mattes Arimidex and Femara so different from tamoxifen. Both of these relatively new drugs are being used as a second line of defense against estrogen-receptor-positive breast cancer, particularly after tamoxifen has stopped working. Based on my experience with women who have used these drugs, Femara appears to be a better choice. |
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Another new drug that is currently being promoted as a breast cancer and osteoporosis preventative, raloxifene, is too new for me to comment on at this time. Like tamoxifen, it works by binding to specific estrogen receptors on the surface of tumor cells where hormones would normally bind, thereby inhibiting tumor-cell growth and reproduction. It seems to produce fewer side effects than tamoxifen, although tamoxifen is still regarded as the standard treatment for breast cancer. |
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In general, chemotherapy is thought to work best in premenopausal women, while hormone therapy works best in postmenopausal women, particularly those whose tumors are hormone-positive. |
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Side Effects of Hormone Therapy |
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The possible side effects of hormone therapy include: |
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Nausea, vomiting, loss of fertility. |
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In women: deepening of the voice, increased libido, increased growth of body hair, menopausal symptoms in premenopausal women, bleeding in post-menopausal women. |
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