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While the drug tamoxifen (brand name, Nolvadex) has long
been prescribed to help prevent a recurrence of breast cancer after treatment, a drug
called Arimidex (generic name, anastrozole) may be
more effective in post-menopausal women. According to study results presented at the
annual San Antonio Breast Cancer Syposium in December 2004, Arimidex reduced the chances
of breast cancer returning after treatment by 26% more than tamoxifen without some of the
potentially severe side effects that can be associated with tamoxifen, such as endometrial
cancer (cancer of the uterine lining). Based on these results, the American Society of
Clinical Oncology (ASCO) Technology Assessment Panel changed its guidelines regarding
early-stage breast cancer treatment. Physicians should now consider a drug like Arimidex,
on its own or in combination with tamoxifen, to prevent breast cancer from returning after
treatment.
In the ATAC (Arimidex, Tamoxifen, Alone, or in Combination) clinical trial, researchers
compared the benefits of Armidiex and tamoxifen in post-menopausal women over a five-year
period. The study involved more than 9,000 women who had been treated for early-stage
breast cancer from 380 cancer centers in 21 countries. The study found that Arimidex was
more effective at preventing the return of breast cancer and was associated with fewer
side effects than tamoxifen, including a reduced risk of endometrial cancer. ATAC is the
largest clinical trial ever conducted to test the two drugs.
Researchers also presented the results of two other studies at the San Antonio Breast
Cancer Symposium. In two European clinical trials, Dr. Raimund Jakesz, of the Vienna
Medical School, and colleagues found that breast cancer patients who switched from
tamoxifen to Arimidex after two years of treatment were less likely to develop breast
cancer again compared to those women who were treated only with tamoxifen after their
initial cancer treatment. The researchers found a decrease in the occurrence of
menopause-like symptoms (such as hot flashes) in the women taking Arimidex. However,
Arimidex did increase the risk of bone fractures.
Taken together, the results of these studies suggest that Arimidex can provide
significant benefits for post-menopausal women who have been treated for breast cancer.
However, data are limited as to whether women should take Arimidex longer than five years.
Nevetheless, ASCO now recommends that physicians consider treating early-stage breast
cancer patients with an aromatase inhibitor such as Arimidex or a combination of an
aromatase inhibitor and tamoxifen to prevent a recurrence of the disease.
Arimidex was first approved by the U.S. Food and Drug Administartion (FDA) in January
1996 as a treatment option for post-menopausal women with advanced breast cancer who have
not responded well to treatment with tamoxifen.
Unlike tamoxifen, which interferes with the ability of cancer cells to use estrogen to
grow and divide, aromastase inhibitors work by inhibiting the body’s conversion of
certain steroid hormones (androgens) to estrogen by the enzyme aromatase. By decreasing
the overall concentration of estrogen in the body, Arimidex helps reduce the spread of
breast cancer in post-menopausal women.
Not all women with advanced breast cancer are candidates for Arimidex therapy. Because
Arimidex decreases the body’s overall level of estrogen, women at high risk of the
bone-thinning disease osteoporosis may not be suited for Arimidex
therapy. Post-menopausal women with advanced breast cancer are encouraged to discuss all
treatment options with their physicians.
The most common side effects of Arimidex include a general feeling of weakness and a
decreased energy level. Other side effects that have been reported with Arimidex include:
- Headache
- Nausea
- Hot flashes
- Mild diarrhea
- Increased or decreased appetite
- Sweating
- Vaginal dryness
- Temporary hair thinning
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