Raloxifene

Raloxifene: Like tamoxifen, raloxifene (Evista®) also blocks the effect of estrogen on
breast tissue. A study comparing the effectiveness of the 2 drugs in women after
menopause, called the Study of Tamoxifen and Raloxifene (STAR) trial, found that
raloxifene worked nearly as well as tamoxifen in reducing the risk of invasive breast
cancer and non-invasive cancer (DCIS). Raloxifene also had lower risks of certain side
effects such as uterine cancer and blood clots in the legs or lungs, compared to tamoxifen
(although the risk of blood clots was still higher than normal). Like tamoxifen, it only
lowers the risk of ER-postive breast cancer and not ER-negative tumors.
Raloxifene is FDA approved to help reduce breast cancer risk in women past menopause
who have osteoporosis (bone thinning) or are at high risk for breast cancer.
Aromatase inhibitors: Drugs such as anastrozole, letrozole, and exemestane are also
being studied as breast cancer chemopreventive agents in post-menopausal women.
These drugs, called aromatase inhibitors, are already being used to help prevent breast
cancer recurrences. They work by blocking the production of small amounts of estrogen
that post-menopausal women normally make. A recent study showed exemestane can
lower the risk of invasive breast cancer by 65% in post-menopausal women who have an
increased risk for breast cancer. Like tamoxifen and raloxifene, exemestane lowered the
risk of breast cancers that are ER-positive, but not those that are ER-negative.
Exemestane and the other aromatase inhibitors can also have side effects, such as causing
joint pain and stiffness. These drugs also can cause bone loss, leading to a higher risk of
osteoporosis. None of these drugs is currently FDA-approved for reducing the risk of
developing breast cancer.
Other drugs: Studies are looking at other drugs as well. For example, some studies have
found that women who take aspirin or non-steroidal anti-inflammatory drugs (NSAIDs)
such as ibuprofen seem to have a lower risk of breast cancer. Studies have also looked to
see if drugs called bisphosphonates may lower the risk of breast cancer. Bisphosphonates
are mainly used to treat osteoporosis, but they are also used to treat breast cancer that has
spread to the bone. These, as well as several other drugs and dietary supplements, are
being studied to see if they can lower breast cancer risk, but none is approved for
reducing breast cancer risk at this time.
Many of the drugs mentioned here are discussed further in the section, "How is breast
cancer treated?" For more information on the possible benefits and risks of
chemopreventive drugs see our document, Medicines to Reduce Breast Cancer Risk.