A new study presented this week at the American Association for Cancer Research (AACR) Breast Cancer Symposium in San Antonio has found that use of the bisphosphonate zoledronic acid (Zometa) increases survival among premenopausal breast cancer patients with estrogen receptor positive (ER+) disease who (1) are at least 40 years old; (2) have undergone ovarian function suppression; and (3) are undergoing endocrine treatment. Bisphosphonates such as Zometa are used primarily to treat osteoporosis. However, they are also given to breast cancer patients to protect against the effects of secondary bone cancer.

Updated results from the ongoing Austrian Breast & Colorectal Cancer Study Group (ABCSG-12) were presented at the symposium by Michael Gnant, MD, professor of surgery and president of the ABCSG at the Medical University of Vienna. To conduct the trial, researches randomly divided 1,803 premenopausal women with early-stage ER+ breast cancer into four groups that received either (1) tamoxifen; (2) Arimidex (anastrozole); (3) tamoxifen plus zoledronic acid; or (4) Arimidex plus zoledronic acid for three years. As of 84 months of follow up, women in the zoledronic acid arms had experienced lower risks of breast cancer recurrence and death compared to the tamoxifen- and Arimidex-only arms, without experiencing toxic side effects. No study participants experienced osteonecrosis of the jaw (the death of bone in the jaw typically occurring as a result of inadequate blood supply) or renal failure. Women aged older than 40 years (with presumed complete ovarian blockade) were found to have a 34% reduced risk of relapse and a 44% reduced risk of death. No significant survival benefits were found for women under 40. The study authors comment that adding zoledronic acid to adjuvant endocrine therapy including ovarian function suppression should be considered for premenopausal women with ER+ early breast cancer.

Study results add to previous positive findings for zoledronic acid

Other studies have also found benefits for the use of zoledronic acid by early stage breast cancer patients:

• Zoledronic acid increases bone mineral density in postmenopausal breast cancer patients receiving the aromatase inhibitor Femara for five years. Postmenopausal breast cancer patients undergoing adjuvant aromatase inhibitor treatment are at risk of progressive bone loss and fractures. Upfront zoledronic acid appears to be a more beneficial treatment strategy than administration that is delayed until signs of reduced bone mineral density become apparent. Long-term coadministration of Femara and zoledronic acid is well tolerated.
• Among women who have completely passed through menopause (five years since last period), those using zoledronic acid experience significantly improved relapse-free survival compared to women in all other age groups (premenopausal, perimenopausal, and unknown status). However, there is a possible increase in recurrence associated with zoledronic acid use in younger women.