Elsevier

Annals of Oncology

Volume 21, Issue 11, November 2010, Pages 2188-2194
Annals of Oncology

original articles
breast cancer
Efficacy of zoledronic acid in postmenopausal women with early breast cancer receiving adjuvant letrozole: 36-month results of the ZO-FAST Study

https://doi.org/10.1093/annonc/mdq217Get rights and content
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Abstract

Background

Aromatase inhibitors (AIs) are accepted as adjuvant therapy for postmenopausal women (PMW) with hormone-responsive early breast cancer (EBC) with superior efficacy to tamoxifen. However, increased bone loss is associated with AIs.

Patients and methods

PMW with EBC receiving letrozole (2.5 mg/day for 5 years) were randomly assigned to immediate zoledronic acid (ZOL; 4 mg every 6 months) or delayed ZOL (initiated only for fracture or high risk thereof).

Results

Patients (N = 1065) had a median age of 58 years; 54% had received prior adjuvant chemotherapy. At 36 months, mean change in L2-L4 bone mineral density (BMD) was +4.39% for immediate versus -4.9% for delayed ZOL (P < 0.0001). Between-group differences were 5.27% at 12 months, 7.94% at 24 months, and 9.29% at 36 months (P < 0.0001 for all). At 36 months, the immediate-ZOL group had a significant 41% relative risk reduction for disease-free survival (DFS) events (P = 0.0314). Adverse events are consistent with the known safety profiles of the study drugs.

Conclusions

At 36 months, immediate ZOL was more effective in preserving BMD during letrozole therapy. Immediate versus delayed ZOL led to significantly improved DFS. Benefits are observed in the context of a favorable, well-established safety profile for letrozole and ZOL.

Keywords

adjuvant therapy
anticancer
aromatase inhibitor
bone loss
breast cancer
survival
zoledronic acid

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