Switching from Tamoxifen to Arimidex ® Improves Outcomes in Breast Cancer
According to results recently presented at the 2003 San Antonio Breast Cancer Symposium, switching to Arimidex ® after at least 2 years of tamoxifen reduces the risk of cancer recurrences compared to continued tamoxifen in postmenopausal women with estrogen-receptor positive breast cancer.
Estrogen-receptor (ER) positive breast cancer refers to a common type of breast cancer that is stimulated to grow by the female hormone estrogen. One common component in the treatment of ER-positive breast cancer is hormone therapy. Hormone therapy works by reducing the levels of circulating estrogen in the body or blocking the growth-stimulatory effects of estrogen on cancer cells. Tamoxifen (Nolvadex ®) is an anti-estrogen type that was the historical standard for ER-positive breast cancer. Recently, however, new agents referred to as aromatase agents have entered the clinical setting as treatment for hormonal therapy for breast cancer and are rapidly gaining momentum as agents used for hormone therapy. Patients responding to tamoxifen are typically treated with the agent for 5 years. Results from clinical trials have demonstrated that outcomes are not improved with use of tamoxifen for over 5 years. In addition, results from a recent clinical trial have indicated that the use of the aromatase agent letrozole (Femara ®) following 5 years of tamoxifen improves outcomes for patients with ER-positive breast cancer.
Recently, researchers from Italy conducted a clinical trial to compare the aromatase agent Arimidex ® (anastrozole) to tamoxifen in patients already treated with tamoxifen. This trial included over 400 postmenopausal women with ER-positive breast cancer, who had already been treated with at least 2 years of tamoxifen. Patients then received either continued tamoxifen for up to 5 years, or Arimidex ® for a comparable duration of time. matched time. At an average follow-up time of approximately 2-3 years, recurrence rates were reduced by over 60% in the group of patients who switched to Arimidex ®, compared to those who continued on tamoxifen. Longer follow-up is necessary to determine if this will correlate with a significant survival difference.
The researchers concluded that it appears that postmenopausal women with ER-positive breast cancer switch to Arimidex ® after at least 2 years of tamoxifen have a significantly reduced rate of cancer recurrences. However, the authors cautioned that larger clinical trials are necessary to confirm this finding and advise this option as a standard approach to treating cancer. Patients who are being treated with tamoxifen may wish to speak with their physician about the risks and benefits of switching over to Arimidex ®.
Reference: Boccardo F, Rubagotti A, Amoroso D, et al. Anastrozole appears to be superior to tamoxifen in women already receiving adjuvant tamoxifen treatment. Proceedings from the 2003 San Antonio Breast Cancer Symposium. December 2003. Abstract #3.