MONDAY, June 6 (HealthDay News) -- Adding zoledronic acid to either anastrozole or tamoxifen improves disease-free survival in women with endocrine-receptor-positive breast cancer who are receiving adjuvant endocrine therapy, according to a study published online June 4 in The Lancet Oncology.
Michael Gnant, M.D., from the Medical University of Vienna in Austria, and colleagues investigated the effect of zoledronic acid on long-term clinical efficacy and disease-free survival in 1,803 premenopausal women with endocrine-receptor-positive breast cancer who were receiving adjuvant endocrine therapy (goserelin) and either tamoxifen or anastrozole. A total of 453 patients were randomly assigned to receive anastrozole alone, while 450 received tamoxifen alone, 450 received anastrozole with zoledronic acid, and 450 received tamoxifen with zoledronic acid, for three years. Participants were followed up for an average of 62 months. Disease-free survival was the primary end point studied. Results were adjusted for eight prognostic variables, and analysis was by intention to treat.
The investigators identified 186 disease-free survival events at follow-up more than two years after completion of treatment. Treatment with zoledronic acid was significantly associated with a reduced number of disease-free survival events (hazard ratio [HR], 0.68), but there was no significant difference between the anastrozole and tamoxifen groups. Zoledronic acid did not significantly impact on the risk of mortality. For patients treated with tamoxifen alone or anastrozole alone, there was no difference in the disease-free survival, but overall survival was worse for those treated with anastrozole alone (HR, 1.75).
"These data show persistent benefits with zoledronic acid and support its addition to adjuvant endocrine therapy in premenopausal patients with early-stage breast cancer," the authors write.
Several authors disclosed financial relationships with the pharmaceutical industry, including AstraZeneca and Novartis, which funded the study.
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