Longer-term follow-of of the ABCSG-12 study continues to suggest that the bisphosphonate drug Zometa® (zoledronic acid) may improve outcomes among women with early-stage, hormone receptor-positive breast cancer. These results were presented at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium.
The majority of breast cancers are hormone receptor-positive. These cancers are stimulated to grow by the circulating female hormones estrogen and/or progesterone. Treatment of hormone receptor-positive breast cancer often involves hormonal therapies that suppress or block the action of estrogen. These therapies include tamoxifen as well as drugs known as aromatase inhibitors.
Zometa is a bisphosphonate drug that is used for the treatment of cancer-related hypercalcemia (high levels of calcium in the blood) and of bone metastases in patients with advanced cancers. Recent research has focused on the potential anticancer effects of Zometa and the ability of Zometa to prevent treatment-related bone loss among women with early-stage breast cancer. Study results regarding the potential anticancer effects of Zometa have been mixed.
The current Phase III clinical trial evaluated Zometa among 1,803 premenopausal women with Stages I-II, hormone receptor-positive breast cancer. The study was conducted by the Austrian Breast and Colorectal Cancer Study Group (ABCSG).
Following surgery all patients were treated with hormonal therapy consisting of goserelin (for ovarian suppression) and either Arimidex® (anastrozole) or tamoxifen. Some patients also received Zometa. Treatment was given for three years.
A previous analysis after four years of follow-up found that women given Zometa had a lower risk of cancer recurrence than women who did not receive Zometa. Women have now been followed for roughly seven years.
- Women treated with Zometa had a 28% relative reduction in risk of recurrence and a 36% relative reduction in risk of death.
- No women experienced osteonecrosis of the jaw (death of bone tissue in the jaw: a rare side effect of some bone drugs).
These results continue to suggest that Zometa may improve outcomes among selected women with early-stage breast cancer. Not all studies have found a benefit of Zometa in early-stage breast cancer, however, and the role of Zometa for this purpose remains uncertain.
Posted December 13, 2011
 Gnant M, Mlineritsch B, Schippinger W, et al. Endocrine therapy plus zoledronic acid in premenopausal breast cancer. New England Journal of Medicine. 2009;360:679-691
 Gnant M, Mlineritsch B, Luschin-Ebengreuth G et al. Long-term follow-up in ABCSG-12: significantly improved overall survival with adjuvant zoledronic acid in premenopausal patients with endocrine-receptor-positive early breast cancer. Presented at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium. December 6-10, 2011. Abstract S1-2.