Endocrine Therapy

Note: Listed below are the drugs used in endocrine therapy and their most common side effects. Other side effects may occur. Please report any persistent or severe problems to your physician.

Aromatase inhibitors are a group of endocrine agents that lower the amount of circulating estrogen in the body. All aromatase inhibitors are tablets that are taken once daily. They should be taken at approximately the same time each day. There are three aromatase inhibitors available:

• Arimidex (Anastrozole)
• Femara (Letrozole)
• Aromasin (Exemestane)

Possible Side Effects

• Hot flashes and sweats – usually mild, decrease with time

Less Common Side Effects

• Vaginal dryness
• Joint pains and stiffness
• Bone fractures

Faslodex belongs to a group of medicines known as hormonal or endocrine therapy. It works as an estrogen receptor blocker. Faslodex is given as an intramuscular injection monthly in women with hormone receptor positive breast cancer that has recurred.

Possible Side Effects

• Hot flashes and sweats - usually mild
• Injection site reaction - pain and redness

Less Common Side Effects

• Diarrhea
• Joint pains and stiffness
• Skin rashes - usually mild

Tamoxifen belongs to a group of drugs known as endocrine agents. It acts as an anti-estrogen in breast tissue by blocking the estrogen required by certain breast cancer cells to grow. Tamoxifen is taken by mouth in a tablet form. It should be taken at approximately the same time each day. Tamoxifen is commonly taken for five years.

Due to potential increased risk of blood clots, Tamoxifen should be discontinued 2-4 weeks prior to major elective surgery. Please discuss further with your surgeon and medical oncologist when to restart tamoxifen.

Possible Side Effects

• Hot flashes
• Vaginal discharge
• Irregular menstrual periods
• Vaginal dryness or itching

Less Common Side Effect

• Skin rash

Rare Side Effects

• Blood clots
• Increased risk of uterine cancers
• Increased risk of cataracts

Zoladex belongs to a group of medicines know as LHRH antagonists. Zoladex ultimately results in a reduction of estrogen production by the ovaries in women. It is used for breast cancer. Zoladex is given by injection under the skin in the abdomen.

Possible Side Effects

• Hot flashes
• Decreased libido (sexual desire)
• Loss of menstrual cycle
• Injection site reactions - redness and soreness