Breast cancer is a malignant disease characterized by an uncontrollable growth of the cells in the breast, largely affecting women. While the exact causes for the development of breast cancer are not fully understood, researchers have identified acquired or inherited gene mutations that cause the disease, as well as numerous risk factors that impact its development.
The female breast is comprised of glands that produce milk and are called lobules; thin tubes that transport the milk from the lobules to the nipple known as ducts; and stroma, which includes both connective and fatty tissue that surrounds the lymph nodes and blood vessels.
There are different types of breast cancer, based on the way cancer cells look under the microscope. A malignant tumor can affect the surrounding tissue or spread to distant areas of the body. The most common type starts in the breast ducts, but the disease can occur in any part of the breast.
Depending on the form of the disease and on the patient’s characteristics, treatment options can include surgery and radiation, which are known as local treatments since they aim to treat the cancer without damaging other parts of the body, or chemotherapy, hormone therapy, targeted therapy, and bone-directed therapy, which are systemic treatments that reach cancer cells anywhere in the body.
How Anastrozole (Arimidex) Works
Anastrozole is a compound classified as an aromatase inhibitor and included in the group of hormone therapies. It is used for the treatment of breast cancer in postmenopausal women, and is being investigated for the treatment of other types of cancer.
In menstruating women, breast cancer growth is promoted by the female sex hormones estrogen and progesterone and can be treated with drugs that block the function of these hormones. After menopause, changes occur in the body, and these drugs are no longer effective. Estrogen is mainly produced by a process known as aromatization, which consists of the transformation of the sex hormones produced by the adrenal glands into estrogen. This process occurs in the fatty tissue, muscle, and skin and it requires an enzyme called aromatase.
Therefore, anastrozole works by blocking the process of aromatization and, consequently, decreasing the levels of estrogen in the body and stopping cancer growth. The National Cancer Institute (NCI) Drug Dictionary defines anastrozole as a “nonsteroidal inhibitor of estrogen synthesis that resembles paclitaxel in chemical structure.
As a third-generation aromatase inhibitor, anastrozole selectively binds to and reversibly inhibits aromatase, a cytochrome P-450 enzyme complex found in many tissues including those of the premenopausal ovary, liver, and breast; aromatase catalyzes the aromatization of androstenedione and testosterone into estrone and estradiol, the final step in estrogen biosynthesis. In estrogen-dependent breast cancers, anastrozole may inhibit tumor growth.”
Anastrozole (Arimidex) for Breast Cancer
Anastrozole was approved by the U.S. Food and Drug Administration (FDA) in January 1996, and it is commercialized by AstraZeneca under the brand name Arimidex. The drug is indicated for postmenopausal women who suffer from early-stage, hormone receptor positive (HR+) breast cancer and who were previously treated with other therapies, who suffer from locally advanced or metastatic breast cancer that is HR+ or hormone receptor unknown as a first-line therapy, or who suffer from advanced breast cancer that has gotten worse after treatment with tamoxifen citrate.
The approval of the drug was based on two clinical trials including 750 patients that revealed the efficacy and safety of anastrozole in advanced breast cancer among postmenopausal women. The treatment plan with anastrozole usually consist on one pill per day at the same time.
About 10 percent of the patients experience side effects like headaches, hot flashes and sweats, feeling sick, skin rashes, painful or stiff joints, swollen joints (arthritis), feeling weak, loss of bone density, mood changes, tiredness or fatigue, and reduced libido. Occasional side effects include bone pain, carpal tunnel syndrome, hair loss, loss of appetite, high cholesterol, feeling sleepy, liver disease, diarrhea, dryness of the vagina, and vaginal bleeding. Rare side effects are inflammation of the liver (hepatitis), and trigger finger.
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