In addition to chemotherapy, another systemic treatment for invasive ductal carcinoma (IDC) is hormonal therapy. Go to “Hormone Receptor Status of Invasive Ductal Carcinoma” to learn more about hormone receptor status, which determines the need for hormonal therapy to treat breast cancer. If your cancer tests positive for estrogen or progesterone receptors, hormonal therapy is almost always included in the treatment plan. Hormonal therapy usually follows chemotherapy and radiation therapy treatments, unless these other systemic and localized treatments are not necessary.

Certain cells located in different parts of the body contain the special proteins that act as hormone receptors. The cells located in the breast are some of these cells – which means breast cancer cells can sometimes contain hormone receptor proteins as well. As the “ears” and “eyes” of the cells, these hormone receptors receive messages transmitted by these hormones as they travel through the bloodstream, telling the cells what they are supposed to do. To put it another way, these hormone receptors act as on/off switches for specific activities within the cells. When the right substance passes through that is compatible with the receptors in the cell, it is like a key fitting a lock – the on/off switch is activated and triggers a specific activity within the cell to begin.

When the cells located in breast tissue contain hormone receptors, progesterone and/or estrogen have a tendency to attach to these receptors and instruct the cells to divide and grow. It is common for the cells within breast cancer to contain high numbers of hormone receptors for progesterone, estrogen, or even both. What this means is that the presence of these hormones gives these cells strong instructions to continue to grow and divide, which causes more cancer cells to develop. When the hormones are taken away or blocked, these cancer cells lose the fuel that accelerates their growth rate, which reduces their chance of survival.

Most hormone therapy is known as anti-estrogen therapy, which works by reducing the amount of estrogen in the body or by blocking the existing estrogen from interacting with the breast cancer cells and telling them to grow. Your doctor will work with you to determine the best form of hormonal therapy for your personal situation. The two types of hormonal therapy that are used most frequently are selective estrogen-receptor response modulators (SERMs) and aromatase inhibitors.

The SERM that many are most familiar with is tamoxifen, which pretends to be estrogen. It then attaches to the estrogen receptors in the breast cancer cells, replacing the role of actual estrogen. The result is that these estrogen receptive cells do not receive the growth signal. Additional examples of SERMs are Fareston (toremifene) and Evista (raloxifene). Although these additional medications are available, tamoxifen is still the go-to medication recommended for women who still have not gone through the process of menopause. However, it can still be used after a woman has gone through menopause.

Aromatase inhibitor medications include Femara (letrozole), Aromasin (exemestane), and Arimidex (anastrozole). These medications reduce the levels of estrogen a woman's body naturally produces after going through menopause. Post-menopausal women receive their estrogen from fat tissue and the adrenal glands instead of their ovaries.

Additional forms of hormonal therapy include estrogen-receptor downregulators (ERDs), which destroy the cells’ estrogen receptors. This blocks the cells from receiving the message to grow from the estrogen that is present. Faslodex (fulvestrant) is an ERD that has been approved for postmenopausal women that have breast cancer to use.

The last form of hormonal therapy for estrogen is to shut down or remove the ovaries, as they are the primary source of estrogen for women who have not gone through menopause. Causing the ovaries to shut down on a temporary basis, for a specified period of time, or even removing them permanently, has the effect of reducing the amount of estrogen a woman has in her body. The treatments for this include the medications Lupron (leuprolide) and Zoladex (goserelin), which are given one time a month via injection over a course of several months to stop estrogen production. For permanent ovary termination, women can undergo one of two procedures. They can either have an oophorectomy, which only removes the ovaries, or a total hysterectomy, which removes the ovaries, fallopian tubes, and uterus.