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Increased risk of liver and endometrial cancer.
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Ocular toxicity56 including decreased visual acuity, macular edema, and other abnormalities that are often reversible after tamoxifen withdrawal. |
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Increased levels of estradiol, the damaging form of estrogen. |
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Increased level of thrombocytes, which can lead to phlebitis, stroke, or blood-clotting disorders. |
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While tamoxifen may show some positive effects on bone mineral density,57 it has also been shown to depress thyroid function.58 |
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Tamoxifen resistance may allow the proliferation of a more aggressive form of cancer that can be difficult to treat. This resistance can develop to the extent that tamoxifen itself actually stimulates cancer growth. It should be noted that tamoxifen is not effective in all estrogen-receptor-positive tumors because it is only a partial antagonist to estrogen.59 |
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Primarily used as hormonal therapy for advanced breast cancer, Megace is also used as a primary treatment for endometrial cancer. It is a synthetic form of the hormone progesterone, which is sometimes used as an estrogen antagonist, particularly when tamoxifen and Arimidex therapies are no longer effective at inhibiting the growth of cancer. It is also used to prevent excessive weight loss or wasting. |
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Another synthetic steroid used in the treatment of endometriosis and benign breast disease, danazol has recently been found to be useful in metastatic breast cancer, specifically in postmenopausal women. It has four mechanisms of action: |
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Inhibition of pituitary gonadotropin secretion |
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Inhibition of adrenal and gonadal steroidogenesis |
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Binding to androgen, estrogen, and progesterone receptors |
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Binding to sex-hormone-binding globulin and corticosteroid-binding globulin60 |
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