Journal of Clinical Oncology, 2008 ASCO Annual Meeting Proceedings (Post-Meeting Edition).
Vol 26, No 15S (May 20 Supplement), 2008: LBA4
© 2008 American Society of Clinical Oncology

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Abstract

Adjuvant ovarian suppression combined with tamoxifen or anastrozole, alone or in combination with zoledronic acid, in premenopausal women with hormone-responsive, stage I and II breast cancer: First efficacy results from ABCSG-12.

Medical University of Vienna, Vienna, Austria; Paracelsus Medical University Salzburg, Salzburg, Austria; Medical University of Graz, Graz, Austria; Hospital of the Sisters of Mercy, Linz, Austria; Medical University of

LBA4

Background: Zoledronic acid (ZOL) has demonstrated antitumor and antimetastatic activity in preclinical and early clinical studies. The Austrian Breast and Colorectal Cancer Study Group Trial 12 (ABCSG-12) examined the efficacy of ovarian suppression using the gonadotropin-releasing hormone analogue goserelin in combination with anastrozole (ANA) or tamoxifen (TAM) ± ZOL in premenopausal women with endocrine-responsive breast cancer (BC). Methods: 1801 premenopausal women with endocrine-responsive BC were randomized to goserelin (3.6 mg q 28 d SC) and TAM (20 mg/d PO) ± ZOL (4 mg IV q 6 mo) or goserelin and ANA (1 mg/d PO) ± ZOL for 3 yr. Primary endpoint was disease-free survival (DFS) for both the comparison of TAM vs ANA and ZOL vs no ZOL, respectively. Relapse-free survival (RFS) and overall survival (OS) were secondary endpoints. Exploratory endpoints included bone-metastases-free survival and safety. Results: With median follow-up of 60 mo (March 31, 2008), 137 (7.6%) DFS events and 42 (2.3%) deaths have occurred. There was no significant difference in DFS between patients who received TAM alone vs ANA alone (HR = 1.10 [95% CI = 0.79, 1.54]; P = .59). However, endocrine therapy plus ZOL significantly reduced the risk of DFS events by 36% compared with endocrine therapy alone (HR = 0.64 [0.46, 0.91]; P = .01). The addition of ZOL significantly reduced the risk of RFS events by 35% (HR = 0.65 [0.46, 0.92]; P = .015) compared with endocrine therapy alone. For OS, there was a nonsignificant trend favoring ZOL treatment (HR = 0.60 [0.32, 1.11]; P = .10). Treatment was generally well tolerated among the 4 groups and consistent with known safety profiles of the drugs. Conclusions: There was no significant difference in DFS between TAM and ANA. The addition of ZOL (4 mg q 6 mo) to adjuvant endocrine therapy significantly prolonged DFS and RFS compared with adjuvant endocrine therapy alone in premenopausal women with endocrine-responsive BC. This large clinical trial demonstrates that the antitumor activity of adjuvant ZOL improves outcomes beyond the effect of endocrine therapy alone.

No significant financial relationships to disclose.

Abstract presentation from the 2008 ASCO Annual Meeting