Hormone therapy for breast cancer

Hormone therapy for breast cancer

Hormone therapy is another form of systemic therapy. It is most often used as an
adjuvant therapy to help reduce the risk of the cancer coming back after surgery, but it
can be used as neoadjuvant treatment, as well. It is also used to treat cancer that has come
back after treatment or has spread.
A woman's ovaries are the main source of the hormone estrogen up until menopause.
After menopause, smaller amounts are still made in the body's fat tissue, where a
hormone made by the adrenal gland is converted into estrogen.
Estrogen promotes the growth of about 2 out of 3 of breast cancers— those having
receptors for the hormones estrogen (ER-positive cancers) and/or progesterone (PRpositive
cancers). Because of this, several approaches to blocking the effect of estrogen
or lowering estrogen levels are used to treat hormone receptor-positive breast cancers.
Hormone therapy does not help patients whose tumors are both ER- and PR-negative.
Tamoxifen and toremifene (Fareston®): These anti-estrogen drugs work by temporarily
blocking estrogen receptors on breast cancer cells, preventing estrogen from binding to
them. They are taken daily as a pill.
For women with hormone receptor-positive cancers, taking tamoxifen after surgery for 5
years reduces the chances of the cancer coming back by about half and helps patients live
longer. A recent study has shown that taking it for 10 years can be even more helpful.
Tamoxifen can also be used to treat metastatic breast cancer, as well as to reduce the risk
of developing breast cancer in women at high risk. Toremifene works like tamoxifen, but
is not used as often and is only approved for patients with metastatic breast cancer.
The most common side effects of these drugs include fatigue, hot flashes, vaginal dryness
or discharge, and mood swings.
Some patients whose cancer has spread to their bones may have a "tumor flare" with pain
and swelling in the muscles and bones. This usually subsides quickly, but in some rare
cases the patient may also develop a high calcium level in the blood that cannot be
controlled. If this occurs, the treatment may need to be stopped for a time.
Rare, but more serious side effects are also possible. These drugs can increase the risk of
developing cancers of the uterus (endometrial cancer and uterine sarcoma) in women who
have gone through menopause. Tell your doctor right away about any unusual vaginal

bleeding (a common symptom of both of these cancers). Most uterine bleeding is not
from cancer, but this symptom always needs prompt attention.
Another possible serious side effect is blood clots, which usually form in the legs (called
deep venous thrombosis or DVT). Sometimes a piece of clot may break off and end up a
blocking an artery in the lungs (pulmonary embolism or PE). Call your doctor or nurse
right away if you develop pain, redness, or swelling in your lower leg (calf), shortness of
breath, or chest pain because these can be symptoms of a DVT or PE.
Tamoxifen has rarely been associated with strokes in post-menopausal women so tell
your doctor if you have severe headaches, confusion, or trouble speaking or moving.
These drugs may also increase the risk of a heart attack, but this is not clear.
Depending on a woman's menopausal status, tamoxifen can have different effects on the
bones. In pre-menopausal women, tamoxifen can cause some bone thinning, but in postmenopausal
women it is often good for bone strength. The effects of toremifene on bones
are less clear.
For almost all women with hormone receptor-positive breast cancer, the benefits of
taking these drugs outweigh the risks.