The Head to Head trial: Letrozole vs anastrozole as adjuvant treatment of postmenopausal patients with node positive breast cancer
10672 Introduction: Aromatase Inhibitors (AIs) have demonstrated both efficacy and safety advantages over tamoxifen (T) in all treatment settings in breast cancer (BC) and are becoming the new standard of care as endocrine therapy for postmenopausal patients (PM) with BC. Rationale: Cumulative evidence suggests that all AIs may not be the same, raising the question of whether there is a superior AI, and whether any specific patient populations derive differing degrees of benefit from a particular AI. In the ATAC trial, evaluating anastrozole (A) in PM patients with early breast cancer (EBC), at 33 months median follow up the risk of recurrence in the hormone receptor positive (HR+) population was reduced by 22%.The BIG 1–98 Trial, evaluating letrozole (L) in PM women with EBC, showed a significant benefit in favor of L over T at a median follow up of 26 months, with a 19% reduction in the risk of recurrence; in subgroup analyses, L significantly decreased the risk of recurrence in LN+ patients and in patients who received adjuvant chemotherapy. This study is a head to head comparison of L and A in HR+, LN+ PM patients with EBC and aims to compare L vs A in the adjuvant treatment of these patients. Design and Methods: This is a Phase IIIb open-label, randomized, multicentre study including 4000 PM patients from up to 250 international sites. PM patients with HR+, LN+ BC who have recently undergone surgery for primary BC will be randomized to either receive L 2.5 mg or A 1 mg daily. Treatment will commence following completion of standard chemotherapy (if given) and concurrently with radiotherapy (if given)Patients will receive treatment until disease recurrence/relapse for up to 5 years. Patients will be stratified by number of LN and HER2 status. The primary objective is disease free survival at 5 years for L and A. Secondary objectives include safety, overall survival, time to distant metastases and time to contralateral breast cancer. Data analysis will be conducted by an independent group of investigators. Summary: Updated patient accrual figures, including any available early safety data, will be presented at the meeting. No significant financial relationships to disclose.