Hormonal (Endocrine) Therapy
What Is Hormonal Therapy?
Hormonal therapy medicines are systemic treatment for hormone-receptor-positive
(HR+) breast cancers. Hormone receptors on breast cells receive signals
from hormones, and "turn on" cell growth and proliferation.
Hormonal therapy medicines treat HR+ breast cancers by either: 1) lowering
the amount of the hormone estrogen in the body, or 2) blocking the action
of estrogen in the body. Because it targets estrogen, hormonal therapy
is also known as anti-estrogen therapy.
Most breast cancers are Hormone Receptor Positive.
- About 80% of breast cancers are estrogen-receptor (ER) positive.
- About 65% of ER positive breast cancers are also progesterone-receptor
- About 13% of breast cancers are ER positive and PR negative.
- About 2% of breast cancers are ER negative and PR positive.
If a cancer is either ER and/or PR positive, it is considered HR positive.
What are the different types of hormonal therapy?
There are three different types of hormonal therapy medicines:
- SERMs (selective estrogen receptor modulators): Tamoxifen
AIs (Aromatase Inhibitors):
- Arimidex (anastrozole)
- Aromasin (exemestane)
- Femara (letrozole)
ERDs (estrogen receptor downregulators): Faslodex(fulvestrant)
- Currently only used in the metastatic setting
Both Tamoxifen and AI are pills taken orally once a day. The ASCO guidelines
were updated in July 2014 and now recommend at least 5 years, and up to
10 years of hormonal therapy.
Who needs hormonal therapy?
Hormonal therapy medicines are used:
- In “high risk” patients who have not been diagnosed with breast
cancer to lower their risk of developing HR positive breast cancer
- In HR positive DCIS breast cancer patients to lower the risk of a local
recurrence or new HR positive breast cancer
- In stage I-III HR positive breast cancer patients to lower the risk of
local or systemic recurrence
- In metastatic HR positive breast cancers to slow the growth and spread
of the cancer
When is hormonal therapy given?
In most cases, hormonal therapy is given after surgery – at the completion
of all surgery, chemotherapy, and radiation. Sometimes, if it is unclear
whether you need chemotherapy or not, but pre-operative therapy is needed
to shrink the tumor, hormonal therapy is prescribed before surgery. Your
doctors will help you decide which timing is best for you.
What are the side effects of hormonal therapy?
In general, hormonal therapy is well tolerated and does not have the toxicity
associated with chemotherapy. The most common side effects of both Tamoxifen
and AI are menopausal symptoms like
hot flashes and mood changes. In addition,
- Tamoxifen is associated with a 1% risk of forming blood clots in your legs
that can travel to your lungs as well as cause a stroke, and a 0.2% risk
of endometrial cancer (cancer of the lining of the uterus).
Aromatase Inhibitors can decrease bone density leading to osteoporosis,
and can cause
body aches or stiffness in the joints.
Often, the side effects become less severe over time. Talk to you doctor
about any side effects you may be experiencing to see what treatment options