Hormone therapy (HT) is used to treat certain cancers that depend on hormones to grow and spread. Patients who undergo this treatment sometimes have surgery or take medications that reduce the levels of certain hormones, such as estrogen (in women) and testosterone (in men). In other cases, patients may take drugs that prevent cancers from receiving the hormones they need to grow.

Hormones are substances produced by one tissue and moved by the bloodstream to another to influence a physiological activity, such as growth or metabolism. They occur naturally in the body, but can also be made synthetically. In some cases, hormone therapy consists of taking medications that suppress the production or interfere with the action of certain hormones. In other cases, surgery may be performed to remove the gland that produces the hormone.

Hormone therapy is used to treat several types of cancer, including:

• Breast cancer
• Ovarian cancer
• Uterine cancer
• Prostate cancer

In most cases, hormone therapy is not a first-line cancer treatment. Instead, it is used in combination with other treatments such as chemotherapy, radiation therapy or after surgery. Hormone therapy sometimes causes side effects, including temporary or permanent infertility. In addition, some cancers become resistant to hormone therapy and begin to grow again after a period of time. Patients with hormone-sensitive cancers should talk with their physician or oncologist about the potential benefits and risks of using a hormone therapy treatment regimen.

Hormone therapy (HT) is a form of cancer treatment that can slow down or arrest cancers – especially breast cancer and prostate cancer – that depend on hormones to grow and spread. In women, estrogen and progesterone are the hormones that most often contribute to cancer. In men, testosterone is the most likely source of stimulus for the cancer.

A hormone is a substance created in an organ, gland or body part that moves through the bloodstream to another body part. The hormone then chemically stimulates the second body part to increase or decrease either functional activity, or the secretion of another hormone. Hormones occur naturally in the body, but can also be made synthetically.

The body’s sex hormones are responsible for regulating reproduction. They also regulate the development of the male and female sexual characteristics. A person’s gonads (ovaries in women, testes in men) create most sex hormones. These are estrogen and progesterone in females and androgens (testosterone and androsterone) in males.

Hormone therapy (HT) associated with cancer differs from hormone replacement therapy (HRT) used to treat menopause in women or the effects of aging in men. In HRT treatments, medications are designed to boost levels of certain hormones in the body. In essence, hormone replacement therapy (HRT) is the opposite of hormone therapy (HT) used to treat cancer. HRT has been implicated in some studies as possibly contributing to some cancers, including those of the breast and ovaries. However, HRT also may lower the risk of other cancers, such as colorectal cancer. Women should weigh the possible benefits and risk of menopausal hormone therapy and discuss them with a physician.

Hormone treatments for cancer aim to reduce the levels of certain hormones in the body. Hormone therapy attacks hormone-sensitive cancer in two ways:

• Reducing the level of hormones in the body. As levels of hormones such as estrogen or testosterone fall, the stimulus for cancer growth dissipates. This can be achieved either by having the patient take medications that suppress hormone production, or by surgically removing the glands that produce hormones.
  
  
• Preventing cancer from using hormones. Synthetic hormones can bind to the cancer’s hormone receptors. HT prevents hormones from reaching and binding to the cancer cells. By preventing the hormones from attaching to the cells, the cancer does not receive the signal from the hormones to grow.

In most cases, hormone therapy will not be the only method of treating cancer. Instead, it is likely to be used in combination with chemotherapy, radiation therapy, surgery or another cancer treatment. Hormone therapy can reach all parts of the body and can affect cancer cells that have spread to areas far from the site of the original cancer.

The different ways in which hormone therapy can be used include:

• Primary treatment. In some cases of advanced (metastatic) cancer, hormone therapy may be used as the main treatment to alleviate symptoms. This occurs most often in patients too ill or elderly to be able to tolerate aggressive therapy.
  
  
• Neoadjuvant therapy. Hormone therapy may be used to shrink a tumor to a more manageable size prior to removing the cancer in surgery. 
  
  
• Adjuvant therapy. In some cases, hormone therapy can be used to prevent cancer from recurring after a tumor has been surgically removed.

While hormone therapy can be an effective means of treating cancer, it has its limitations. Most advanced cancers that depend on hormones can become resistant to hormone therapy and find a way to grow without the use of hormones. In such instances, physicians may switch patients to non-hormonal therapy.

Some physicians may prescribe intermittent doses of hormones as a way to keep a patient’s cancer from becoming resistant to hormone therapy. For example, the vast majority of prostate cancers treated with hormone therapy become resistant to the medication over a period of years. By using hormone therapy intermittently (for example, six months on and six months off), many physicians believe they can lessen the chances that this resistance will develop in the patient. In some cases, physicians may switch the patient to a different hormone therapy drug after a period of time. Changing the schedule or drug also may help reduce the incidence and severity of side effects associated with hormone therapy.

Certain rare cancers may cause excessive levels of hormones in a person’s body. This can cause various symptoms, ranging from sweating to high blood pressure. Hormone-blocking drugs may be prescribed to treat such conditions, which can be triggered by cancers such as carcinoid tumors, small cell lung cancer, pheochromocytomas (tumors of the adrenal gland) and other neuroendocrine cancers (small, slow growing tumors found mostly in the gastrointestinal system).

Hormone therapy can be administered to cancer patients by several different methods. These include:

• Drugs. Various medications can alter the body’s production of estrogen and testosterone or block the ability of the hormone to stimulate the cancer. These drugs can be taken orally or by injection.   
  
  
• Surgery. Surgery can substantially reduce the levels of a hormone in the body by removing the part of the body that produces the hormone. However, some of these hormones are produced in reproductive organs. Surgery may be a less acceptable alternative for many, especially those who are young and are still considering having children. Certain drugs can mimic the effect of such surgery, often making surgery unnecessary.
  
  Removal of the following organs is sometimes ordered as part of hormone therapy:
  
  
• • Testicles (orchiectomy or castration)
  • Ovaries in premenopausal women (oophorectomy)
  • Adrenal gland in postmenopausal women (adrenalectomy)
  • Pituitary gland in women (hypophysectomy) [rare]
    
    
• Radiation. Suppresses the production of hormones, and – as in surgery – is usually targeted to the testicles, ovaries, adrenal gland or pituitary gland. Radiation is sometimes recommended when surgery appears to be either too risky or likely to cause too many side effects.

Patients with certain types of cancer are especially likely to benefit from hormone therapy (HT).

Cancer cells have hormone receptors that bind to certain hormones that stimulate their growth. However, not all cancers use hormones for growth. If the cancer uses hormones to grow, the cancer is labeled “receptor positive” or “hormone dependent.” If the cancer does not rely on hormones to grow, it is labeled “receptor negative” or “hormone independent.” Cancers that are receptor positive benefit from hormone-blocking therapy because the drugs block the hormones from stimulating the cancer. 

For example, the common hormone-blocking drug tamoxifen is effective in treating breast cancers that are receptor positive. The drug prevents the hormone from stimulating the cancer by blocking its attachment to the cancer cells. Typically, the more estrogen receptors that are present, the more likely the patient will respond to hormone therapy. Tamoxifen is not a treatment for receptor negative cancers because those cancers do not rely on hormones to grow. 

Some cancers are more sensitive to hormone therapy than others, and sensitivity can vary even within a particular type of cancer. A sample of a tumor (biopsy) can be analyzed in a laboratory to determine whether or not that tumor is likely to respond to hormone therapy.

Cancers that are often receptive to hormone therapy include:

• Breast cancer
• Ovarian cancer
• Uterine cancer
• Prostate cancer

While hormone therapy can be an effective form of cancer treatment, it also carries some risks. Those who have surgery may lose all or part of an organ. Other side effects are more likely to be temporary and differ depending on a patient’s gender, including: 

Men (estrogen administration or testosterone deprivation):

• Decreased sexual desire
• Enlarged breasts
• Hot flashes
• Inability to achieve an erection
• Incontinence
• Osteoporosis

Women (estrogen deprivation):

• Fatigue
• Hot flashes
• Mood swings
• Nausea
• Osteoporosis
• Weight gain
• Decreased sexual desire

Certain uncommon cancers may cause excessive levels of other hormones. Symptoms that may accompany such high hormone levels include:

• Sweating
• Flushing
• High blood pressure
• Diarrhea

There is also some evidence that taking hormone therapy drugs like tamoxifen over long periods of time may actually cause the patient to become resistant to their benefits. However, this is not the case with all hormone therapy drugs. Patients should speak with their physician about the possible long-term benefits and risks of various hormone therapy medications.

A great deal of research is being conducted in hormone therapy (HT), particularly for breast cancer, women's reproductive cancers and prostate cancer. Research has focused on the use of new drugs for treatment, effective combination of HT drugs with each other or with other therapies and length of drug usage.

Recent research has studied the use of aromatase inhibitors for the treatment of certain cancers. Unlike tamoxifen which prevents the body from using estrogen, aromatase inhibitors prevent the body from producing the hormone. In a study released in 2005, the National Cancer Institute (NCI) reported the results of a large clinical trial in which women took an aromatase inhibitor following their course of treatment with tamoxifen. The study suggested that survival rates for women with early stage breast cancer improved with the use of an aromatase inhibitor following tamoxifen.

Additional research has suggested that early stage brest cancer patients may benefit from switching from tamoxifen to an aromatase inhibitor during treatment. Those who changed after two or three years of tamoxifen may have an increased chance of survival and experience fewer side effects of hormone therapy. More research is needed to evaluate the effectiveness of this course of treatment.

Other studies have shown that patients with an aggressive form of breast cancer who took aromatase inhibitors combined with biological therapy had longer periods of time where their disease did not progress. More research is needed to determine the role of these drugs in the treatment of cancers, as well as their potential risks.

Other research in hormone therapy has included:

• Use of vaccines with antiandrogen therapy for prostate cancer treatment
  
  
• Improved understanding of estrogen receptors and response to hormone therapy
  
  
• New hormone therapy drugs
  
  
• Optimal length of treatment with drugs
  
  
• Combining hormone therapy with chemotherapy for treatment
  
  
• Rotating hormone therapy drugs to reduce the risk of resistance
  
  
• Differences of activity of  drugs in pre- and post- menopausal women
  
  
• Long-term effects of hormone therapy and cancer recurrence
  
  

In addition, hormone therapy is being studied in conjunction with tumor marker tests and genetics to determine their role in treatment.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to hormone therapy (HT):

1. How does hormone therapy work?
   
   
2. Do I have the type of cancer that could benefit from HT?
   
   
3. Which tests can tell me if I am a candidate for HT?
   
   
4. Would HT involve surgery? If so, what type?
   
   
5. When would I start HT medications and for how long?
   
   
6. How do you decide which type of HT drug I should use?
   
   
7. Can I take this drug with other medications?
   
   
8. How will it affect how I feel?
   
   
9. What are the short and long term side effects of HT?
   
   
10. What happens if I stop taking the drug earlier than prescribed?
    
    
11. What can I do to help ease the side effects of hormone therapy?
    
    
12. Will side effects from the drug continue after I stop using HT?
    
    
13. Will HT prevent my cancer from recurring?
    
    
14. How can you tell if HT is working?