Hormone Therapy

What are hormones and how are they used as therapy?

Hormones are chemicals that are naturally produced by the organs making up the body’s endocrine system (including the pancreas, as well as pituitary, thyroid and adrenal glands). These chemicals travel throughout the body via the bloodstream, coordinating the functions of various organs from head to toe. Hormones are responsible for regulating the function of just about every cell in the body. Some examples of hormones include: estrogen, testosterone, insulin, thyroid hormone, cortisol, and epinephrine.

Researchers have determined that some cancers are “fueled” by hormones, and may rely upon them to grow. In these cases, blocking the action of these hormones could possibly stop the cancer from growing. There are a few ways in which this can be achieved:

• Block the hormones from acting: Cells have “receptors” on their surface where certain hormones bind and subsequently trigger activity inside the cells. By blocking the receptor with another compound, the hormone is not able to connect to its receptor. So if the hormone’s normal “parking spot” on the cell is already occupied, the hormone cannot attach to and activate the cell.
• Prevent the body from producing the hormone: This can be done with medication to block production of the hormone, or with surgery to remove the organ that produces it. For example, estrogen production can be significantly decreased by surgically removing the ovaries.
• Eliminate the hormone receptors on cells or change their shape: This makes it impossible for the hormone to properly attach itself to the cell receptor and to activate it, essentially making the hormone unable to function.

Hormone therapy that is used to treat certain cancers should not be confused with hormone replacement therapy. Hormone therapy is used to block hormones or their actions, whereas hormone replacement therapy, which is not a cancer treatment, generally refers to giving menopausal women hormones to replace the ones the body no longer makes in order to treat menopause-related symptoms.

How is hormone therapy given?

Hormone therapy is most often used to treat breast and prostate cancers, where its role is well established through numerous clinical trials. Meanwhile, research is ongoing to study the potential efficacy of hormonal manipulation in treating other cancer types. Hormone therapy can be given in a few ways:

• Oral medication – some therapies are taken by mouth
• Injection – some therapies are given by an injection under the skin (subcutaneous) or in the muscle (intramuscular)
• Surgical intervention – for example, removal of the ovaries in women, or testicles in men, results in decreased production of certain hormones.

Many patients think of hormone therapy as being “less potent” than chemotherapy, but it can be just as effective in certain breast and prostate cancers. Hormone therapy is considered a “systemic” therapy, meaning that it travels throughout the body. Surgery or radiation therapy are considered “local” treatments.

What are the side effects of hormone therapy?

The side effects are caused by the lack of whatever hormone is being blocked or inactivated. For women, these effects are similar to those experienced with menopause, which is the body’s natural decline in estrogen production with age. Side effects can include: hot flashes, night sweats, weight gain, vaginal dryness, and headache. Some side effects are caused by the hormone therapy. These can include: nausea, hair loss or thinning, muscle aches and joint pain, and, more seriously, blood clots and increased risk of uterine/endometrial cancer.

In men, the side effects can include hot flashes, tiredness, breast tenderness or enlargement, nausea, loss of sex drive, and impotence.

This decrease in the body’s natural hormones can put men and women at higher risk for developing osteoporosis. Bisphosphonate therapy may be used to counteract this side effect. In addition, your healthcare provider may recommend taking steps to decrease the risk or severity of osteoporosis. This may include increasing calcium and vitamin D intake through diet or supplements, participating in weight bearing exercise and avoiding tobacco and alcohol use (which increases osteoporosis risk). Learn more about bone health and cancer.

How do I know if hormone therapy is working for me?

This answer varies, depending on the type of cancer being treated. Many patients will have radiology studies (CT scans, MRI scans, PET scans) periodically to assess the tumor’s response (shrunk, stayed the same, or grown). Some types of tumors can be followed using a specific “tumor marker”. This is a substance that is either produced directly by the tumor, or by the body in response to the tumor, and can be measured by a blood test. If the therapy is working, one would expect the tumor marker level to decrease. In some cases, a decrease in a patient’s symptoms may be able to signal if the medications are shrinking the tumor or not. Talk with your healthcare provider about your specific situation.

Classes of Hormone Therapy

Anti-Estrogens

An antiestrogen or estrogen blocker works by blocking estrogen receptors in breast tissue. While estrogen may not actually cause breast cancer, it is necessary for the cancer to grow in some breast cancers. With estrogen blocked, the cancer cells that feed off estrogen may not be able to survive.

Generic Name	Brand Name	Action
tamoxifen	Nolvadex®	Anti-estrogen
toremifene	Fareston®	Anti-estrogen
fulvestrant	Faslodex®	Estrogen receptor antagonist

Side Effects

Every person reacts differently to medications, so it is difficult to predict what side effects each patient will experience. However, the most common side effects in this category of medications include hot flashes, night sweats, weight gain, vaginal drynessand nausea. Blood clots and endometrial cancers are rare, but can occur with these medications.

Aromatase Inhibitors

In women who have gone through menopause, estrogen is mainly produced by converting androgens (sex hormones produced by the adrenal glands) into estrogens. An enzyme called aromataseis responsible for this conversion. Aromatase inhibitors block this conversion, leading to less estrogen in the body.

Generic Name	Brand Name	Action
anastrozole	Arimidex®	aromatase inhibitor
letrozole	Femara®	aromatase inhibitor
exemestane	Aromasin®	aromatase inactivator

Side Effects

Every person reacts differently to medications, so it is impossible to predict what side effects each patient will experience. However, common side effects in this category of medications include hot flashes, night sweats, headache, nausea, hair thinning, vaginal dryness, muscle aches and joint pain.

Other Hormone Treatments Used for Breast Cancer

Hormone sensitive breast cancers can also be treated with other hormone agents.

Generic Name	Brand Name	Action
Fluoxymesterone	Halotestin®	Androgen, works by opposing the activity of estrogen
Megestrol Acetate	Megace®	A form of progesterone, works by interfering with cell growth in ER+ cells.
Leuprolide for women	Lupron®	LHRH agonist, works by stopping production of leutinizing hormone by the pituitary gland. LH causes the ovaries to make estrogen.

Anti-Androgens

Most prostate cancers need supplies of the male hormone testosterone to grow. Testosterone is an androgen produced by the testes and adrenal glands. The production of testosterone can be stopped by surgically removing the testicles or through medication therapy. Anti-androgens work by blocking testosterone receptors, and therefore preventing testosterone from attaching to the receptors on the surface of the prostate cancer cells. Without testosterone, the cancer cells may either grow more slowly, or stop growing altogether. You may hear this treatment called androgen deprivation therapy or ADT.

Generic Name	Brand Name	Action
bicalutamide	Cased®	anti-androgen
nilutamide	Nilandron®	anti-androgen
flutamide	Eulexin®	anti-androgen

Side Effects

Every person reacts differently to medications, so it is difficult to predict what side effects each patient will experience. However, the common side effects for this category of medications include hot flashes, breast tenderness, nausea, loss of sex drive and impotence.

Luteinizing Hormone Releasing Hormone Agonist (LHRH Agonist)

A hormone called luteinizing hormone, produced by the pituitary gland, stimulates the testicles to produce testosterone. LHRH agonists stop the production of luteinizing hormone by the pituitary gland. This reduces the production of testosterone in men. The cancer cells may then grow more slowly or stop growing altogether. These are sometimes called gonadotropin-releasing hormone blockers (GnRH blockers). You may hear this treatment called androgen deprivation therapy or ADT.

Generic Name	Brand Name	Action
Goserelin for Men	Zoladex®	LHRH agonist
Goserelin for Women	Zoladex®	LHRH agonist
Degarelix	Firmagon®	GnRH antagonist
Leuprolide for men	Lupron®	LHRH agonist
Leuprolide for women	Lupron®	LHRH agonist

Side Effects

Every person reacts differently to medications, so it is difficult to predict what side effects each patient will experience. However, common side effects in this category of medications include tiredness, breast tenderness, nausea, loss of sex drive, and impotence.

Ref: OncoLink