Randomized study of every six-month versus single-dose adjuvant zoledronate in early breast cancer

The multicenter ReaCT-ZOL trial in Canada randomized postmenopausal patients with early breast cancer (EBC) to receive a single infusion of zoledronate 4 mg intravenously (n=107) or an infusion every 6 months for 3 years (n=104). Three-year results showed that a single infusion was associated with increased patient convenience, less toxicity, and lower rates of treatment discontinuation. Final prespecified 5-year follow-up results have now been published. At 5 years, there were no clearly apparent differences between for recurrence-free survival (88.7% versus 84.1%; HR 0.71; 95% CI 0.34-1.51), bone metastasis-free survival (90.6% versus 86.0%; 0.68; 0.30-1.52), or overall survival (91.6% versus 88.0%; 0.79; 0.34-1.82) in the single-infusion group versus the group receiving infusions every 6 months. At 5 years, there were no significant differences in the incidence of osteonecrosis of the jaw (0% versus 0%) or fragility fractures (5% versus 2%). The authors conclude that at 5 years, there was no evidence of a difference in survival outcomes between the treatment approaches.