Tamoxifen and anastrozole as a sequencing strategy in postmenopausal women with hormone-responsive early breast cancer: updated data from the Austrian breast and colorectal cancer study group trial 8.

CTRC-AACR San Antonio Breast Cancer Symposium: 2008 Abstracts Abstract #14 Background : Historically, standard endocrine treatment for postmenopausal women with hormone-sensitive early breast cancer (EBC) was 5 years' tamoxifen. However, the inclusion of an aromatase inhibitor (AI) is now considered standard practice. There is increasing evidence that whether as initial adjuvant treatment or as a switch treatment following 2-3 years of tamoxifen therapy, Ais improve patients' outcomes compared with 5 years' tamoxifen monotherapy. To date, there is limited evidence comparing a prospective sequencing strategy of 2 years of tamoxifen followed by 3 years of an AI compared with 5 years' tamoxifen. Previously presented data from ABCSG Trial 8 (SABCS 2005), at a median follow-up of 55 months, revealed a 24% reduction in the risk of recurrence in favor of a sequencing strategy compared with 5 years' tamoxifen (hazard ratio [HR] 0.76; 95% confidence interval [CI] 0.56-1.02), although the difference was not statistically significant (p=0.07). Here we present updated data from ABCSG Trial 8. Methods : Postmenopausal women with histologically verified G1 or G2, locally radically treated invasive or minimally invasive hormone receptor-positive breast cancer were eligible for inclusion. Newly diagnosed patients were randomized to receive 5 years' tamoxifen therapy or 2 years' tamoxifen followed by anastrozole for 3 years. The primary endpoint was event-free survival, including locoregional and distant metastatic recurrences and new contralateral breast cancers. Results : This final analysis will report the data cut-off point, the number of eligible patients, and the median follow-up period of the trial, which will exceed 5 years. The incidence of first events, local recurrences, distant metastases, and contralateral breast cancers for the two treatment arms of the study will be presented. The effect of treatment on the trial endpoint will be analyzed using a Cox proportional hazards model and data will be presented as estimated HRs with two-sided 95% CIs and p-values. Conclusions : The updated analyses of ABCSG Trial 8 will provide evidence regarding 2 years' treatment with tamoxifen followed by 3 years' anastrozole in comparison to 5 years' tamoxifen for postmenopausal women with newly diagnosed hormone-sensitive EBC. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 14.