Primary results from EMILIA, a phase III study of trastuzumab emtansine (T-DM1) versus capecitabine (X) and lapatinib (L) in HER2-positive locally advanced or metastatic breast cancer (MBC) previously treated with trastuzumab (T) and a taxane.

LBA1 Background: T-DM1 is an antibody-drug conjugate comprising T, a stable linker, and the potent cytotoxic agent DM1; it incorporates the antitumor activities of T and the HER2-targeted delivery of DM1. Methods: EMILIA is a randomized study of T-DM1 vs XL, the only approved combination for T-refractory HER2+ MBC. Patients (pts) received T-DM1 (3.6 mg/kg IV q3w) or X (1000 mg/m2 PO bid, days 1–14 q3w) + L (1,250 mg PO daily) until progressive disease (PD) or unmanageable toxicity. Pts had confirmed HER2+ MBC (IHC3+ and/or FISH+), and prior therapy with T and a taxane. Primary end points were PFS by independent review, OS and safety. An interim OS analysis (efficacy boundary: HR= 0.617; p=0.0003) was planned at the time of the final PFS analysis. Results: 991 pts were enrolled; 978 received treatment. Median (med) durations of follow-up were 12.9 (T-DM1) and 12.4 (XL) months (mo). Baseline demographics, prior therapy and disease characteristics were balanced. There was a significant improvement in PFS fav...