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52

NCCN Guidelines for Patients

®

:

Breast Cancer – Locally Advanced (STAGE III)

Version 1.2017

6

Endocrine therapy

Overview

Endocrine therapy stops cancer growth

caused by hormones. Part 6 explains the

types of endocrine therapy and which

ones are options for you. It also provides

some details on what to expect during

endocrine therapy.

Overview

Estrogen and progesterone help some breast

cancers to grow. These cancers are described as

hormone receptor–positive. Most breast cancers

are hormone receptor–positive. Endocrine therapy

is a standard treatment. It lowers the chance of the

cancer returning.

Some people refer to endocrine therapy as hormone

therapy. However, hormone therapy can then be

confused with hormone replacement therapy. The

former treats breast cancer whereas the latter treats

menopausal symptoms.

Endocrine therapy can be received with some but

not all cancer treatments. It’s okay to take HER2

antibodies during endocrine therapy. Endocrine

therapy may be started during or after radiation

therapy. Endocrine therapy is usually given after

chemotherapy is finished.

If you are pregnant, don’t start endocrine therapy. It

may harm your baby. Start after your baby is born.

Types of endocrine therapy

Endocrine therapy affects female hormones by one

of two methods. Some therapies block hormones

from working. Others lower hormone levels in the

body. The main types of endocrine therapy are

described next. The section,

Treatment guide

, lists

which ones may be an option for you.

Aromatase inhibitors

lower estrogen levels in the

body. These drugs block a protein that changes a

hormone (androgen) into estrogen. They do not

affect estrogen made in the ovaries. See

Guide 9

for a complete list of drugs for hormone-related

growth.

Antiestrogens

stop the effect of estrogen on

cell growth. SERMs (

s

elective

e

strogen

r

eceptor

m

odulators) attach to estrogen receptors and block

estrogen from attaching. SERDs (

s

elective

e

strogen

r

eceptor

d

egraders) block and destroy estrogen

receptors.

See Figure 14

.

Ovarian ablation

permanently stops the ovaries

from making hormones. Most often, both ovaries

are removed from the body. This surgery is called a

bilateral oophorectomy. Radiation to the ovaries also

stops the making of hormones, but isn’t commonly

used.

Ovarian suppression

temporarily stops the

ovaries from making hormones. It is achieved with

drugs called LHRH (

l

uteinizing

h

ormone-

r

eleasing

h

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

hormones.