NCCN Guidelines for Patients
Breast Cancer - Early-Stage
(STAGES I AND II)
, Version 1.2016
What to expect
also stops the ovaries from making estrogen and
progesterone, but isn’t used often.
For many women, endocrine therapy causes
symptoms of menopause. Menopausal symptoms
include hot flashes, vaginal discharge or dryness,
sleep problems, weight gain, hair thinning, fatigue,
and changes in mood. Which symptoms you will have
may differ from other women.
Tamoxifen also has two rare but important side
effects. They are cancer of the uterus and blood clots.
For most women with breast cancer, the benefits of
taking tamoxifen far outweigh the dangers.
Aromatase inhibitors don’t cause cancer and very
rarely cause blood clots. However, they can weaken
your bones (osteoporosis) and cause bone fractures.
Checking your bone health with regular bone mineral
density tests can show bone weakness before
fractures occur. Your doctor can order medicine
to strengthen your bones if necessary. Aromatase
inhibitors can also cause joint pain in some women.
Not all the side effects of endocrine therapy are listed
here. Please ask your treatment team for a list of all
common and rare side effects. If a side effect bothers
you, tell your treatment team. There may be ways to
help you feel better.
Figure 6.1 Antiestrogens
Antiestrogens are drugs that stop the effect of estrogen on cancer cell growth. Tamoxifen is an
antiestrogen that is commonly used for stages I and II breast cancer. It blocks estrogen from
attaching to its receptor and starting cell growth.
Tamoxifen blocks estrogen
so cell growth isn't triggered
Estrogen binds to receptors
and triggers cell growth