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AstraZeneca, the maker of tamoxifen (brand name,
Nolvadex), a drug used to both treat and prevent breast cancer, has added new information
to the drug’s labeling in the past year, warning of potential health risks. The
warning is aimed particularly at women at high risk of breast cancer who are considering
tamoxifen as well as those women who have been diagnosed with an early form of breast
cancer called ductal carcinoma in situ (DCIS). The drug maker
warns of an increased risk of uterine cancer from tamoxifen, as well as higher risks of stroke and blood clots.
AstraZeneca provides the following warning about tamoxifen (Nolvadex):
"In clinical trials it has been shown that cancer of the uterus, stroke, and blood
clots can occur approximately 2 to 4 times more frequently with Nolvadex than placebo, but
each occurred in less than 1% of women. Some of these strokes, blood clots, and uterine
cancers were fatal.
"For most women with breast cancer, the benefits of Nolvadex outweigh its risks.
If you are taking Nolvadex to reduce your risk of developing breast cancer because you are
at high risk or have DCIS, you should discuss these warnings with your healthcare
provider."
Though tamoxifen has long been associated with a slight increased risk of uterine
cancer—usually endometrial cancer, which involves the uterine lining—there is
new information that tamoxifen may also increase the risk of uterine sarcomas (cancer of
the body of the uterus). Though uterine carcinomas are rare (they account for 2% to 5% of
uterine cancer cases), they tend to be diagnosed at later stages, when the chances of
successful treatment and survival are lower.
According to the American Cancer Society, approximately 39,300 new cases of uterine
cancer are diagnosed in the United States each year. Endometrial cancer is the most common
form of uterine cancer, accounting for approximately 95% of all uterine cancers.
Endometrial cancer (cancer of the uterine lining), pulmonary embolism (blood clots in
the lungs), and stroke are also serious but generally rare side effects of tamoxifen.
These usually occur in less than 1% of women who take the drug. Less severe side effects
of tamoxifen include hot flashes and vaginal irritation.
AstraZeneca recommends that women report any unusual vaginal discharge, vaginal
bleeding, or menstrual irregularities; or pain or pressure in the pelvis (lower stomach)
to their physicians immediately. Women taking tamoxifen should also receive yearly
gynecological examinations.
Despite the new labeling, the benefits of tamoxifen typically outweigh the relatively
small risk of the drug for the majority of women, particularly those who use it to treat
their breast cancer. Studies have shown that tamoxifen can help reduce breast cancer risk
by as much as 50% in some women at high risk for the disease. For this reason, tamoxifen
is currently the only drug approved by the U.S. Food and Drug Administration (FDA) to
reduce breast cancer risk in women without the disease.
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