Anastrozole inhibits the estrogen-dependent growth of breast cancer. The active ingredient is mainly used in postmenopausal women and in men as part of endocrine therapy (anti-hormone therapy) for estrogen-sensitive breast cancer.
What is anastrozole?
As a benzyltriazole derivative, anastrozole belongs to the active ingredient group of non-steroidal aromatase inhibitors. It is primarily used for the adjuvant (supportive) therapy of breast cancer in women during and after the menopause.
The active ingredient inhibits the synthesis of estrogen, which is an important growth factor for the mostly hormone-sensitive cells of breast cancer. In addition to tumor growth, anastrozole reduces the risk of metastasis (spread of tumor cells in the rest of the body) and the risk of recurrence (recurrence of the disease).
Although the male organism has only small amounts of estrogen or synthesizes it, men can also get breast cancer. These are usually also treated with aromatase inhibitors such as anastrozole.
Pharmacological effect
The effect of anastrozole is based on the inhibition of aromatase. Aromatase is an enzyme that catalyzes the conversion of androgens (male sex hormones) to estrogens (female sex hormones). Estrogen promotes tumor growth and metastasis in estrogen-sensitive cancers such as breast cancer. Aromatase inhibitors such as anastrozole intervene in this mechanism by binding them to the aromatase. The enzyme is inactivated and enzymatic catalysis is prevented.
As a result, the estrogen level drops, the tumor cells have less estrogen available and growth is slowed down. In premenopausal women (before menopause), hormone conversion by aromatase takes place mainly in the ovaries (ovaries). Aromatases can also be found in the liver, adrenal glands and adipose tissue cells. However, since aromatase inhibitors are ineffective in the ovaries, estrogen synthesis cannot be blocked by anastrozole. During the menopause, aromatase activity in the ovaries is gradually stopped.
The aromatase and consecutively the estrogen concentration drops considerably here, while this remains in the other tissue cells. If breast cancer cells develop that also produce aromatase, additional tumor-promoting estrogen is formed in the body. In the tumor cells, adrenal glands, adipose tissue cells and in the liver, the aromatases can be blocked by anastrozole and the growth of estrogen-sensitive tumors can be slowed down or stopped accordingly.
Medical application & use
Anastrozole is used as part of the adjuvant, endocrine therapy of estrogen-sensitive breast cancer and for the therapy of progressive (advanced) breast cancer in postmenopausal women.
Studies (including ATAC study 2008) have shown that the use of anastrozole after primary therapy (usually surgery with subsequent radiation and / or chemotherapy) in postmenopausal women reduces the risk of recurrence by an average of 24 percent and the risk of disease-free Survival time can be extended by about 15 percent.
In addition, adjuvant anti-hormone therapy can extend the time until distant metastases and contralateral tumors (on the complementary side of the body) occur. Generally, there are two basic treatment strategies available. On the one hand, anastrozole can be applied directly after the surgical procedure (upfront therapy). On the other hand, anastrozole can only be used after two to three years of postoperative therapy with tamoxifen (estrogen receptor modulator) (switch therapy).
Due to the lack of studies on the comparability of the two strategic approaches, an individual decision is made as to which strategy to pursue in the context of endocrine therapy. There is also a lack of data on the optimal duration of treatment. In many cases, prolonged therapy over 5 years is recommended.
Risks & side effects
Since aromatase inhibitors such as anastrozole do not affect the effects of other hormones or enzymes, they are relatively well tolerated. A side effect of anastrozole therapy is, in particular, a decrease in bone density with a correspondingly increased risk of fractures and accompanying joint pain.
Increasing the intake of vitamin D and calcium is recommended to reduce these symptoms. Bone density should be measured regularly in people who are at increased risk of osteoporosis. Fatigue, shortness of breath, vomiting, nausea, hair loss, skin rash and dry vaginal mucous membranes are other possible side effects of anastrozole therapy. Occasionally, loss of appetite, vaginal bleeding and high blood cholesterol may be observed.
Treatment with anastrozole is contraindicated before the menopause, in the case of pronounced kidney dysfunction and moderate to severe liver disease. Estrogens cancel the effects of anastrozole. The application of estrogen-containing drugs (including vaginal suppositories) should be avoided accordingly.
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