Aromatase inhibitors for early-stage breast cancer
In breast cancer, new, malignant tissue starts growing in a mammary gland. If the cancer remains within a limited area around the breast and doesn't spread to other parts of the body (metastasis), it is referred to as early-stage breast cancer. Some of the breast lymph nodes may also be affected.
Women who have early-stage breast cancer have several treatment options, depending on the type of tumor, their individual health circumstances and their personal preferences. The standard treatment is to try to surgically remove as much of the tumor as possible. Additional (adjuvant) therapy – in the form of radiation, hormone therapy or chemotherapy – can be used to try to kill any remaining cancer cells.
About two thirds of all women with breast cancer have a hormone-sensitive tumor. This means that like estrogen influence how fast the cancer cells grow. If the cancer cells have receptors that the can attach to, the tumor is referred to as hormone-receptor-positive breast cancer (HR-positive or HR+). Anti-hormone therapy is a possible treatment for hormone-receptor-positive cancer. This aims to slow down tumor growth.
Anti-hormone therapy can work in several ways, including the following:
- By blocking hormone receptors on the cancer cells: The drug tamoxifen is similar to estrogen. When it is used, it blocks certain hormone receptors that are also found on the cancer cells, so that the natural estrogen in the body can no longer attach to them.
- By inhibiting estrogen production: After menopause, most of the estrogen in women's bodies is produced in the adrenal glands and in muscle and fat tissue. There it is needed for the production of an enzyme called aromatase. Drugs such as anastrozole, extemestane and letrozole block aromatase, thereby preventing the production of estrogen in the body. That is why they are called aromatase inhibitors. Before menopause, estrogen is mainly produced in the ovaries. The aromatase inhibitors are ineffective there, though. So younger women who have not yet entered menopause are first treated with the drug tamoxifen.