Zoledronic acid reduces risk for recurrent breast cancer in premenopausal patients with early-stage disease who have undergone surgery and are receiving ovarian suppression and hormone therapy, according to a presentation at the annual meeting of the American Society of Clinical Oncology.

All women in the multicenter phase III trial had cancer that was positive for estrogen receptors, progesterone receptors, or both.

"It's very exciting to find that in addition to preventing bone loss in women undergoing adjuvant endocrine therapy for breast cancer, zoledronic acid can also reduce the likelihood that breast cancer will return in some women," said Michael Gnant, MD, a professor of surgery at the Medical University of Vienna, the president of the Austrian Breast and Colorectal Cancer study group, and the study's lead author.

"Future research will focus on optimizing the administration schedule and the dose, and determining which patients will benefit the most from treatment with zoledronic acid."

The study randomized 1,803 patients with stage I or II disease who were receiving postoperative ovarian suppression using goserelin to one of four arms: treatment with tamoxifen or anastrozole with or without zoledronic acid.

The study's primary endpoint was disease-free survival. After a median follow-up of 60 months, hormone therapy plus zoledronic acid reduced the risk of relapse by 35 percent compared with hormone therapy alone. There was not a significant difference between the two hormone therapies. Treatment was well tolerated in all four groups and there were no unexpected side effects.