Abstract P2-13-04: Superior efficacy of anastrozole to tamoxifen as adjuvant therapy for postmenopausal patients with hormone-responsive breast cancer. Efficacy results of long-term follow-up data from N-SAS BC 03 trial

Abstract

Abstract Background: Aromatase inhibitors have been shown to be superior to tamoxifen as adjuvant therapy in postmenopausal patients with hormone-responsive breast cancer. Here we report the efficacy results of long-term follow-up data from N-SAS BC 03 trial (UMIN CTRID: C000000056), in which anastrozole was compared to tamoxifen in hormone-responsive postmenopausal early breast cancer patients who had taken tamoxifen for 1—4 years out of a total of 5 years of treatment as adjuvant therapy. Patients and methods: Out of a total of 706 recruited patients, 696 patients (tamoxifen group, n=345; anastrozole group, n=351) were used as the full analysis set for the present study. The log-rank test was used to compare the two groups in terms of disease-free survival (DFS) and relapse-free survival (RFS), Kaplan-Meier estimates were calculated. The treatment effects were estimated by Cox's proportional hazard model and were expressed as hazard ratios, with associated 95% confidence intervals (CIs). Results: After a median follow-up of 76.1 months, (range: 1.3–110 months), the unadjusted hazard ratio was 0.87 (95%Cl 0.60–1.26; log-rank p = 0.457) for DFS and 0.77 (95%Cl 0.49–1.22; log-rank p = 0.266) for RFS, both in favor of anastrozole. The estimated hazard ratio (95%CIs) for DFS and for RFS until each time point (right censored data) was as follows: until 30 months: 0.54 (0.30–0.98) and 0.48 (0.23–0.98), until 42 months; 0.65 (0.40–1.06) and 0.53 (0.29–0.97), until 54 months: 0.77 (0.50–1.19) and 0.63 (0.37–1.06), until 66 months: 0.82 (0.55–1.24) and 0.72 (0.44–1.17), until 78 months: 0.83 (0.57–1.23) and 0.73 (0.46–1.17), respectively. The hazard ratios (95%CIs) for DFS and for RFS until 36 months were 0.72 (95%Cl 0.43–1.22) and 0.58 (95%Cl 0.30–1.12), and those after 36 months were 1.06 (95%Cl 0.62–1.81) and 0.98 (95%Cl 0.51–1.88), respectively. Conclusion: Superior efficacy of anastrozole to tamoxifen in the Japanese population was suggested over a long-term follow-up period. It was the greatest early after switching from tamoxifen and then decreased thereafter. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-13-04.