SAN ANTONIO, Dec. 9 /PRNewswire/ -- Postmenopausal women with hormone- sensitive breast cancer receive an increased benefit from treatment with the aromatase inhibitor anastrozole compared with tamoxifen, according to two papers presented on Wednesday, December 08, 2004, at the 27th Annual San Antonio Breast Cancer Symposium. Benefits were seen whether anastrozole was given as a primary treatment for five years, or as an additional treatment after two years of tamoxifen.
Aromatase inhibitors deplete circulating estrogen in postmenopausal women, shutting down the principal cell signaling pathway in the pathogenesis of breast cancer. Tamoxifen, in comparison, exerts its effect by interacting with the estrogen receptor.
Dr. Tony Howell from the University of Manchester reported the five-year results of the ATAC (Arimidex [anastrozole], Tamoxifen, Alone, or in Combination) trial, which was designed to compare the benefits of anastrozole versus tamoxifen given over a five-year period. Data are now available for a total of 9,366 patients from 381 centers in 21 countries, at a median follow- up time of 68 months. Significant improvement was seen in disease-free survival, time to recurrence, and occurrence of contralateral breast cancer in the anastrozole arm compared with the tamoxifen arm.
Dr. Raimund Jakesz from the Vienna Medical School reported the combined results of two European trials (ARNO 95 and ABCSG8), which together included 3,123 patients. Of these, 1,560 received tamoxifen for five years, and 1,563 were switched to anastrozole after an initial two years on tamoxifen. At 28 months median follow-up, the event-free survival (with events defined as locoregional recurrence, distant metastases, and contralateral breast cancer) was 95.8% in the tamoxifen-anastrozole arm compared with 92.7% in the tamoxifen arm.
In both studies, there was an increase in the rate of bone fractures in patients receiving anastrozole, but a decrease in side effects normally associated with tamoxifen treatment (hot flashes, vaginal bleeding and discharge, etc.). In other studies being presented at the symposium, researchers are reporting the successful use of bisphosphonates to preserve bone mineral density in patients receiving aromatase inhibitors.
It now seems clear that patients receive a significant benefit from anastrozole treatment, whether it is given as primary treatment or after two years of tamoxifen treatment. We do not yet know which of these approaches will yield better results, or if anastrozole should be continued for longer than five years.
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San Antonio Breast Cancer SymposiumCONTACT: Marybeth Libonate of M2 Communications, +1-201-433-9400, forSan Antonio Breast Cancer Symposium