Understanding hormone therapy

Hormone therapy falls into 2 broad groups, explains Medical Oncologist Dr Jason Naicker:

1. To block your body's ability to produce hormones.
2. To interfere with how hormones behave in your body.

There are two main reasons that you may be prescribed hormone therapy as part of your treatment plan:

1. To treat your cancer - in which case it can lessen the chance. that your cancer will return or to stop or slow its growth.
2. To ease your cancer symptoms.

Hormone therapy may be given before your surgery or radiation therapy to make the tumour smaller (called neoadjuvant therapy), after your main cancer therapy (called adjuvant therapy), or if your cancer has already spread.

Types of hormone therapy

Breast cancer hormone therapy

The female hormones oestrogen and progesterone affect some breast cancers. Doctors describe these cancers as oestrogen receptor positive (ER+) or progesterone receptor positive (PR+) or both. Hormone treatment for breast cancer works by stopping these hormones getting to the breast cancer cells.

Tamoxifen is one of the most commonly used hormone therapies for breast cancer. It can be taken by both premenopausal and post-menopausal women and works by blocking the oestrogen receptors on breast tissue.

Aromatase inhibitors may be prescribed if you have been through the menopause. After menopause, your ovaries stop producing oestrogen but your body still makes a small amount by changing other hormones into oestrogen. Aromatase is the enzyme that makes this change happen.

Luteinising hormone (LH) blockers may be prescribed if you are premenopausal. Your pituitary gland produces luteinising hormone (LH) which controls the amount of hormones made by your ovaries and LH blockers stop its production of luteinising hormone by blocking the signal to your ovaries which then stop making oestrogen or progesterone.

Prostate cancer hormone therapy

Prostate cancer depends on testosterone to grow. Hormone therapy blocks or lowers the amount of testosterone in your body which can lower the risk of an early prostate cancer coming back when you have it with other treatments or can shrink an advanced prostate cancer or slow its growth.

Luteinising hormone (LH) blockers block the signal from your pituitary gland to your testicles so your testicles stop making testosterone.

Anti-androgens
Prostate cancer cells have testosterone receptors to which testosterone attaches and encourages the cells to divide so that the cancer grows. Anti-androgen drugs work by attaching to these receptors and preventing testosterone from reaching the prostate cancer cells.

Gonadotrophin releasing hormones (GnRH) blockers stop messages from a part of your brain called the hypothalamus that tell your pituitary gland to produce luteinising hormone. So blocking GnRH stops your testicles from producing testosterone.

There are other newer hormonal treatments for prostate cancer that your doctor may discuss with you.

Womb cancer hormone therapy

Both oestrogen and progesterone affect the growth and activity of the cells that line your womb. Doctors use progesterone treatment to help shrink larger womb cancers or to treat womb cancers that have come back.

How is Hormone Therapy administered?

The drugs can either be a tablet or an injection. Hormonal therapy may even include surgery to remove organs that produce hormones (ovaries in women, and testicles in men).

How long will you be on hormonal therapy?

This can vary depending on the treatment you're taking, and will be discussed by your doctor. It may be for a few months to a few years.

What are the side effects?

Because hormone therapy blocks your body's ability to produce hormones or interferes with how hormones behave, it can cause unwanted side effects. Remember that everyone is different, says Dr Naicker, so you may or may not experience these common side effects. These include:

For men who receive hormone therapy for prostate cancer:

• Hot flashes
• Loss of interest in or ability to have sex
• Weakened bones
• Enlarged and tender breasts
• Fatigue

For women who receive hormone therapy for breast cancer include:

• Hot flashes
• Vaginal dryness
• Changes in your periods if you have not yet reached menopause
• Loss of interest in sex
• Fatigue

How to Tell If Hormone Therapy Is Working?

If you are taking hormone therapy for prostate cancer, you will have regular PSA tests. If hormone therapy is working, your PSA levels will stay the same or may even go down.

If you are taking hormone therapy for breast cancer, you will have regular check-ups. Check-ups usually include an exam of the neck, underarm, chest, and breast areas. You will have regular mammograms, though you probably won't need a mammogram of a reconstructed breast. Your doctor may also order other imaging or lab tests to monitor your progress.