Interim joint analysis of the ABC (anthracyclines in early breast cancer) phase III trials (USOR 06-090, NSABP B-46I/USOR 07132, NSABP B-49 [NRG Oncology]) comparing docetaxel + cyclophosphamide (TC) v anthracycline/taxane-based chemotherapy regimens (TaxAC) in women with high-risk, HER2-negative breast cancer

1000Background: The ABC adjuvant trials (5/2007-11/2013) were developed by USOR and NSABP to determine if a regimen of TC for 6 cycles is non-inferior to combination regimens of doxorubicin/cyclophosphamide with docetaxel or paclitaxel (TaxAC) in women with resected high-risk, HER2-negative breast cancer. 1870 patients (pts) from B-49 were combined with 1077 from the TaxAC and TC groups of B-46-I/USOR 07132, and 1295 from USOR 06-090, for a total of 4242. A detailed history of this collaborative effort will be discussed. Methods: The primary endpoint was invasive disease-free survival (iDFS), defined as time to local, regional or distant recurrence, invasive contralateral breast cancer, second primary cancer, or death. Pts were stratified for: parent trial, pos nodes (0, 1-3, 4-9, 10+), and hormonal status (neg, pos). A hazard ratio (HR) from a stratified Cox model of 1.18 or more was pre-defined as inferior. HRs above 1 favor TaxAC. Our pre-specified interim monitoring plan was to report early for futili...