Hormone Therapy for Breast Cancer Treatment—Starving The Cells That Kill

Posted by Medical Board on October 17, 2017 in Hormones Women
Hormone Therapy for Breast Cancer Treatment—Starving The Cells That Kill

Sometimes a mammogram detects breast cancer. Other times, you or your physician discover a lump. No matter how you find out you have it… it’s always a shock.
One in eight U.S. women will be diagnosed with breast cancer in her lifetime. One in 37 will die from the disease.[5] Many women however, will find effective treatment for breast cancer through hormone therapy administered by an oncologist. The type and stage of breast cancer found will help guide specific treatment protocols and aftercare follow-ups.

Getting the most current, accurate information available is critical at the onset of breast cancer diagnosis. When breast cancer strikes you can’t afford to waste time.
Hormone Therapy for Breast Cancer

To understand how hormone therapy works for breast cancer, it is important to know how hormones function in general. Hormones travel through the bloodstream, acting as chemical messengers. These affect cells and tissues at several levels and locations within the body.

Primary Sex Hormones in Women

Estrogen and progesterone are produced primarily in the ovaries of women. Estrogen works to develop and maintain female sex characteristics, as well as to stimulate the growth of long bones in the body. Progesterone controls menstruation and supports pregnancy as well.

The Role of Hormones in Breast Cancer

In addition to the primary roles of estrogen and progesterone in female development and pregnancy, hormones also promote the growth of some breast cancers, referred to as “hormone-sensitive” or “hormone dependent”. The cells of hormone-sensitive breast cancers contain proteins that act as receptors when hormones bind to them. The receptors once activated cause changes in the expression of specific genes. These can stimulate cancer cell growth.[2]

What is hormone therapy?

Hormone therapy works to treat breast cancer by either slowing or stopping the growth of hormone-sensitive tumors.

Hormone therapy is considered “systemic therapy” because it affects cancer cells throughout the body, not just those located in the breast.[3] It does this in one of two ways. It either hampers the body’s ability to produce certain hormones, or interferes with the way hormones act on breast cancer cells.

*Tumors categorized as “hormone insensitive” will not respond to hormone therapy at all.

Breast Cancers Responsive to Hormone Therapy

Estrogen receptor positive (ER positive) refers to those cancer cells that are directly affected or sensitive to estrogen. Roughly 80% of breast cancers are ER positive. The majority of tumor cells containing estrogen receptors also contain progesterone receptors. These are known as progesterone receptor positive (PR, or PgR positive). Breast tumors that contain both estrogen and progesterone receptors are sometimes called hormone receptor positive (HR positive). In order to determine if breast cancer tumors contain receptors for either estrogen or progesterone, doctors test samples of tumor tissue that has been surgically removed.

Hormone Therapy Types

Hormone-sensitive breast cancer may be treated utilizing a number of different strategies.

Block ovarian function—By suppressing ovarian function, estrogen levels are reduced, essentially “cutting off” the fuel supply for cancerous tumors. This can be done permanently with ovarian oblation (removal of the ovaries) either surgically, or with radiation. Temporary ovarian suppression can be achieved with drugs called gonadotropin-releasing hormone (GnRH) agonists, which may also be referred to as luteinizing hormone-releasing hormone (LH-RH) agonists. These drugs block communication between the pituitary gland and ovaries so that estrogen is not produced.

Block estrogen production— Aromatase inhibitors are drugs used to block a specific enzyme known as “aromatase” necessary for the production of estrogen. These are used primarily in postmenopausal women because premenopausal women produce too much estrogen for efficacy.

Blocking effects of estrogen—Many drugs interfere with the effects of estrogen and can be administered to suppress the growth of breast cancer cells. These include selective estrogen receptor modulators (SERMs) that stop estrogen from binding, as well as other anti-estrogen drugs that target estrogen receptors for destruction.[3]

How Hormone Therapy Works

The type of therapy received is dependent on the stage of breast cancer, whether or not the patient is pre or postmenopausal, and previous treatment outcomes.

Most hormone receptor-positive breast cancers are treated for a period of 5 to 10 years with endocrine therapies administered orally or through injection.[6] Hormone therapy is conducted three main ways.

Adjuvant therapy in early-stage breast cancer—Hormone therapy is administered to women for a period of time (at least 5 years) after surgical removal of cancerous breast tissue. This greatly reduces the risk for recurrence in the same or other breast. Specific drugs or types of drugs may be alternated depending on whether a woman is pre or postmenopausal, and how effective past pharmacological treatment has been.

Advanced treatment for metastatic breast cancer—Various combinations of drugs may be used to treat recurrent breast cancer, metastasized cancer, or breast cancer that has worsened after other hormone therapies.

Neoadjuvant treatment of breast cancer—Hormone treatment may be administered to patients to shrink cancerous breast tissue before a surgical procedure.

* Aromatase inhibitor therapy before surgery can allow for breast conservation surgery (lumpectomy) rather than a mastectomy in some cases where receptor-rich tumors are found.[7]

Hormone Therapy for Prevention

Some drugs have been FDA approved for the prevention of breast cancer. These may be administered to women who are at increased risk for developing the disease. Several studies indicate that five years of preventive hormone therapy can reduce the incidence of breast cancer for up to 20 years thereafter.

Other Hormone Therapies

Other hormone therapies that have been used historically are rarely administered now.

These include the following:
Megestrol acetate (Megace) (mimics progesterone)
Androgens (male hormones)
Estrogen in high doses[3]

These are sometimes used if mainstream hormone therapies are ineffective.
Hormone Therapy Side Effects
It is important to weigh the benefits of hormone therapy with the side effects in order to make the most informed decision about treatment. A number of side effects occur in drugs associated with hormone therapy for breast cancer. Because of this, medical professionals may rotate, alternate, or stop specific drugs altogether to balance therapeutic benefits with negative side effects.

Common side effects include:

Hot flashes, night sweats, and vaginal dryness. The menstrual cycle is also affected by hormone therapy.

Serious (less common) side effects for specific drugs may include:


Blood clots (lungs and legs)
Endometrial cancer
Uterine cancer (yearly pelvic exam recommended)[4]
Bone loss
Mood swings
Decreased sex drive

Skin rash
Decreased sexual interest


Blood clots (lungs, legs)
Ovarian suppression
Bone loss
Mood swings
Decreased sex drive
Aromatase inhibitors
Heart attack
Heart failure
Hypercholesterolemia (high cholesterol)
Bone loss
Joint pain
Mood swings

Gastrointestinal difficulties

Hormone Therapy Interactions

Some medications may render hormone therapy ineffective or less effective including:

Selective serotonin reuptake inhibitors (SSRIs) for depression
Quinidine for abnormal heart rhythms
Diphenhydramine an antihistamine
Cimetidine a stomach acid inhibitor

Hormone therapy is an effective treatment option for millions of Americans with breast cancer, with new medications tested every day. Finding the right combination of drugs to stop or slow the growth of cancer cells in the body is the objective of every therapeutic regimen.

1Benner, Julia D. “Medical Treatments.” Medical Treatments – UVA Cancer Center, 8 June 2017, cancer.uvahealth.com/cancers-we-treat/specialty-programs-clinics/breast-cancer-program/breast-cancer-treatments/medical-treatments. 
2“Hormone Therapy for Breast Cancer.” National Cancer Institute, www.cancer.gov/types/breast/breast-hormone-therapy-fact-sheet. 
3“Hormone Therapy for Breast Cancer.” American Cancer Society, www.cancer.org/cancer/breast-cancer/treatment/hormone-therapy-for-breast-cancer.html. 
4“Hormone Therapy for Cancer Treatment.” Hormone Therapy For Cancer Treatment – Health Encyclopedia – University of Rochester Medical Center, www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=85&contentid=p07236. 
5“How Common Is Breast Cancer?” American Cancer Society, www.cancer.org/cancer/breast-cancer/about/how-common-is-breast-cancer.html. 
6Iacorossi, L, et al. “Adherence to hormone therapy in women with breast cancer: a quantitative study.” Professioni infermieristiche., U.S. National Library of Medicine, www.ncbi.nlm.nih.gov/pubmed/27600553. 
7“Preoperative Hormone Therapy May Preempt Need for Mastectomy Among Postmenopausal Breast Cancer Patients.” University of Maryland Medical Center, www.umm.edu/news-and-events/news-releases/2012/preoperative-hormone-therapy-may-preempt-need-for-mastectomy-among-postmenopausal-breast-cancer-patients.

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