Drug Switch Beneficial in Early Breast-Cancer
Switching drugs from tamoxifen to anastrozole in women with early-stage breast cancer may reduce the risk of disease recurrence or spread by up to 40%, according to an article by Reuters concerning an Austrian medical study.
Anastrozole belongs to the drug class of aromatase-inhibitors, which block the estrogen production in women. Estrogen is linked with cancer development. Anastrozole is sold under brand name Arimidex and manufactured by AstraZeneca.
Tamoxifen interferes with the activity of estrogen and for over 20 years has been a standard post-surgical treatment for women with hormone-sensitive tumors.
According to the National Cancer Institute, “breast cancer is the most common non-skin cancer and the second leading cause of cancer-related death among women.” In women, most cases of cancer occur in the post-menopausal years.
In the tamoxifen-anastrozole study, scientists at the Vienna Medical University in Austria reported that varying tamoxifen therapy with anastrozole produced better outcomes in post-menopausal women.
"Switching from tamoxifen to anastrozole after two years is more beneficial for the patients than staying on tamoxifen," said Professor Raimund Jakesz, the lead researcher, according to Reuters.
Clinical Study Results
The study, published in The Lancet, examined the effects of two types of treatment on >3,000 women participating in two trials. All women received tamoxifen for about two years, after which half of the women were randomly assigned anastrozole for three years, while the other half remained on tamoxifen.
Jakesz and colleagues reported that, after a two-year follow-up, the women who received anastrozole had up to a 40% reduction in risk of recurrence and of breast cancer in their other breast.
Anastrozole is limited; it does not work in younger women and may increase the risk of bone-fractures. In the group of women receiving anastrozole, more had broken bones, but fewer had blood clots.
"Although further investigation is necessary...this analysis confirms that post-menopausal women who receive tamoxifen as adjuvant therapy should be switched to anastrozole after two years of treatment," Jakesz commented.
In another study, published in the British Medical Journal, researchers at the University of Sydney in Australia reported that a woman’s risk of developing breast cancer after taking hormone replacement therapy (HRT) (often taken to relieve menopausal symptoms) might be lower than previously believed.
In this study, the researchers found that HRT only slightly increases a woman’s cumulative risk of the disease. Use of estrogen only, and of estrogen and progestogen combined hormone-therapy, at age 50 for about 5 years, had minimal impact on risk. In contrast, women on combined therapy for 10 years had an increased cumulative absolute risk of 7.7%.
Previous research suggested that combined hormone therapy could double a woman’s usual risk of developing breast cancer. In Europe, combined HRT is preferred over single-hormone HRT because it reduces the risk of cancer of the womb, which is linked with estrogen-only HRT.
Sources:
Drug switch helps women with early breast cancer, Reuters, 4
August 2005.
Switching of postmenopausal women with endocrine-responsive early
breast cancer to anastrozole after 2 years’ adjuvant
tamoxifen: combined results of ABCSG trial 8 and ARNO 95 trial.
The Lancet, Volume 366, pages 455-462, 2005.
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