Hormone Therapy for Breast Cancer

Medical Video: Adjuvant Hormonal Therapy for Estrogen Receptor Positive Early Stage Breast Cancer

Hormone therapy (also known as hormonal therapy, or endocrine therapy) blocks the body's ability to produce hormones or by interfering with the action of hormones to slow or stop the growth of hormone-sensitive tumors.

Hormone therapy for breast cancer is not the same as menopausal hormone therapy or female hormone replacement therapy, where hormones are given to reduce menopausal symptoms. Hormone therapy is most often used as adjuvant therapy to help reduce the risk of cancer coming back after surgery and neoadjuvant treatment. It is also used to treat cancer that has recurred after treatment or has spread.

Several strategies have been developed to treat hormone-sensitive breast cancer, including the following:

Blocking ovarian function. Examples of ovarian suppression drugs are goserelin (Zoladex®) and leuprolide (Lupron®).
Blocking estrogen production: A drug called aromatase inhibitors can be used to block the activity of an enzyme called aromatase, which the body uses to make estrogen in the ovaries and other tissues. Examples of anastrozole aromatase inhibitors (Arimidex®) and letrozole (Femara®), both of which temporarily deactivate aromatase, and exemestane (Aromasin®), which permanently stop enzyme activity.
Blocking the effects of estrogen: Some drugs interfere with the ability of estrogen to stimulate the growth of breast cancer cells: Selective estrogen modulator receptors (SERM) binds to estrogen receptors, prevents estrogen from binding. Examples of SERMs are tamoxifen (Nolvadex®), raloxifene (Evista), and toremifene (Fareston®). Tamoxifen has been used for more than 30 years to treat positive hormone receptor breast cancer. Other antiestrogen drugs, such as Fulvestrant (Faslodex®), work in a somewhat different way to block the effects of estrogen.

How does hormone therapy work?

Most of the estrogen in a woman's body is made by the ovary. After menopause, smaller amounts are still made in body fat tissue, where hormones made by the adrenal gland are converted to estrogen.

Estrogen makes receptor breast cancer positive for growth hormones. About 2 of the 3 types of positive hormone receptor breast cancer contain estrogen hormone receptors (ER-positive cancer) and / or progesterone (PR-positive cancer). So, reducing the amount of estrogen or blocking its work can reduce the risk of recurrence of breast cancer in the early stages after surgery. Hormonal therapy drugs can also be used to help reduce or slow down the growth of advanced or positive hormone receptor breast cancer metastases. This type of treatment is beneficial for receptor-positive breast cancer hormones, but it does not help tumor patients with negative hormone receptors (both ER- and PR-negative).

Hormone therapy prevents cancer cells from getting the hormones they need to grow and slow or stop the growth of positive hormone receptor tumors. This is done in several ways.

Some hormone therapies, such as the tamoxifen drug, attach to receptors in cancer cells and block estrogen from sticking to receptors. Other therapies, such as aromatase inhibitors, reduce the level of estrogen in the body so that cancer cells cannot get the estrogen they need to grow.

What are the side effects of hormone therapy?

Side effects of hormone therapy depend on certain drugs or types of treatment. Your doctor will consider the benefits and risks of using hormone therapy and choose the best treatment for you.

Heat, night sweats, and vaginal dryness are common side effects of hormone therapy. Hormone therapy also interferes with the menstrual cycle in premenopausal women.

It is rare but a serious side effect of hormone therapy drugs might include:

Tamoxifen

Risk of blood clots, especially in the lungs and legs
Stroke
Cataract
Endometrium and uterine cancer
Bone loss in premenopausal women
Mood changes, depression, and loss of libido
In men: headache, nausea, vomiting, skin rash, impotence, and decreased sexual interest

Raloxifene

Risk of blood clots, especially in the lungs and legs
Stroke in certain subgroups

Ovarian suppression

Bone loss
Mood changes, depression, and loss of libido

Aromatase inhibitors

Risk of heart attack, angina, heart failure, and hypercholesterolemia
Bone loss
Joint pain
Changes in mood and depression

Fulvestrant

Gastrointestinal symptoms
Losing power
Pain

The general change strategy, in which patients use tamoxifen for 2 or 3 years, followed by aromatase inhibitors for 2 or 3 years, can produce a balance between the benefits and harms of both types of hormone therapy.

What should I worry about?

Certain drugs, including some antidepressant prescriptions, inhibit an enzyme called CYP2D6. This enzyme plays an important role in the use of tamoxifen by the body because it metabolizes, or divides, tamoxifen into molecules, or metabolites, which are far more active than tamoxifen itself.

The possibility that SSRIs, inhibiting CYP2D6, slowing down metabolism of tamoxifen and reducing its potential is a concern given that as many as a quarter of breast cancer sufferers experience clinical depression and can be treated with SSRIs. In addition, SSRIs are sometimes used to treat burning sensation caused by hormone therapy. Other drugs that inhibit CYP2D6 include the following: