Several studies have looked at the effects of anastrozole in women with breast cancer.
One large study looked at anastrozole for the adjuvant treatment of early breast cancer. Adjuvant therapy for breast cancer is treatment that follows breast cancer surgery (with or without radiation). It is given to help prevent the cancer from returning. These studies compared anastrozole with tamoxifen (Nolvadex, Soltamox) in postmenopausal women with hormone receptor-positive cancer.
After five years, up to 17 percent more women taking anastrozole were cancer-free, compared to those taking tamoxifen. In this particular study, women taking anastrozole were also less likely to stop the medicine because of side effects when compared to women taking tamoxifen. This study also showed that taking both breast cancer medications together did not offer any advantage.
Two other large studies compared anastrozole to tamoxifen in postmenopausal women with advanced or metastatic breast cancer. These women had tumors that were either hormone receptor-positive or the receptor status was not known.
In these studies, anastrozole was at least as effective as tamoxifen in how the cancer responded to the medication (either by shrinking the tumor or stopping its growth) and time to progression. "Time to progression" is a medical term that means from the time that the cancer is treated until the disease starts to get worse, such as when the cancer spreads (metastasizes) or the tumor increases in size.
For these studies, time to progression was, on average, up to 11.1 months for anastrozole and, on average, up to 8.3 months for tamoxifen.
There were also two studies that showed anastrozole may be effective for treating advanced breast cancer that has not responded to tamoxifen in postmenopausal women. These studies included women who had breast cancer that was hormone receptor-positive. Women with hormone receptor-negative breast cancer were included only if they had originally responded to treatment with tamoxifen.
Written by/reviewed by: Kristi Monson, PharmD;Arthur Schoenstadt, MD
Last reviewed by: KristiMonson, PharmD;
List of references (click here):
Arimidex [package insert]. Wilmington, DE: AstraZeneca Pharmaceuticals LP;2009 April.
Food and Drug Administration, Center for Drug Evaluation and Research. Electronic orange book: approved drug products with therapeutic equivalence evaluations. FDA Web site. Available at: http://www.fda.gov/cder/ob/. Accessed July 1, 2010.
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