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NCCN Guidelines for Patients


Breast Cancer - Early-Stage


, Version 1.2016


Endocrine therapy

What to expect

What to expect

There are four main types of endocrine therapy.

Not all types will work for every woman. The types

of treatment that may work for you depend on your

menopausal status.

In general, menopause is the point in time when you

won’t have another menstrual period again. Breast

cancer doctors also define menopause as when the

ovaries aren’t able to make high levels of estrogen.

If you had your ovaries removed (oophorectomy)

you are postmenopausal. If you had your uterus

removed (hysterectomy), you may need blood tests

to confirm your menopausal status. If you have these

female organs but didn’t have a menstrual period

the year before cancer treatment, you are likely


If you get menstrual periods, you are premenopausal.

If you were premenopausal before starting

chemotherapy, the absence of menstrual periods after

chemotherapy doesn’t mean you’re postmenopausal.

Your ovaries may still be working despite no

menstrual periods or may start working again. To

confirm your menopausal status, the amount of

estrogen or FSH (






ormone) in your

blood needs to be tested.

Estrogen is mostly made by the ovaries and made

in small amounts by the adrenal glands, liver, and

body fat. Progesterone is also mostly made by the

ovaries. The ovaries are the main source of estrogen

and progesterone only in women who have menstrual

periods (premenopausal). Endocrine therapy either

blocks hormones from working or lowers hormone

levels by targeting the main source.


Antiestrogens are drugs that stop the effect of

estrogen on cancer cell growth. These drugs

can be used among both premenopausal and

postmenopausal women. Tamoxifen is an

antiestrogen that is commonly used for stages I and II

breast cancer.

As shown in

Figure 6.1

, tamoxifen treats breast

cancer by attaching to the estrogen receptors and

blocking estrogen from attaching. This type of

antiestrogen is called a SERM (








odulator). It is a pill that is taken every day

during the course of treatment.

Aromatase inhibitors

Aromatase inhibitors are drugs that lower estrogen

levels in the body. These drugs work by blocking

a protein that makes estrogen in postmenopausal

women. They can’t stop the ovaries in premenopausal

women from making estrogen. For this reason, these

drugs are only used among women after menopause

caused by age or treatment. Three drugs in this

category are: anastrozole (Arimidex


), letrozole



), and exemestane (Aromasin


). Each is

a pill that is taken every day during the course of


Ovarian suppression

Ovarian suppression lowers the amount of estrogen

in the body among premenopausal women. It

is achieved with drugs called LHRH (








ormone) agonists. LHRH is a

hormone in the brain that helps control the making of

estrogen by the ovaries. LHRH agonists stop LHRH

from being made, which stops the ovaries from

making more estrogen. Goserelin (Zoladex


) and

leuprolide (Eligard


, Lupron


) are LHRH agonists and

are given as monthly injections under the skin.

Ovarian ablation

Ovarian ablation is the removal or destruction of

the ovaries. This treatment stops the ovaries from

making estrogen in premenopausal women. Surgery

that removes both ovaries is called a bilateral

oophorectomy. Radiation therapy to the ovaries