1047 Background: The addition of carboplatin (Cb) to paclitaxel (P) and trastuzumab (T) improves response rate and time to progression (TTP) in HER2+ MBC (Robert N, JCO 2006). Weekly P+Cb+T is active and well-tolerated in patients (pts) with HER2+ MBC (Perez E, Clin Breast Cancer 2005). Nab-P is more active than Cremophor-based P (Gradishar W, JCO 2005). This study investigates the efficacy and safety of weekly nab-P+Cb+T. Methods: An initial cohort of 3 pts received nab-P at 75 mg/m2 i.v. followed by Cb at a target AUC=2 weekly (days 1, 8, 15 every 28 days) + T (4 mg/kg x 1, then 2 mg/kg on all weeks) for 1 cycle. This was well tolerated, thus nab- P was escalated to 100 mg/m2 for all subsequent cycles and pts. Neither prophylactic steroid nor antihistamine was given. Due to hypersensitivity reactions (HSRs) clearly attributable to Cb in 4 of the first 13 pts, Cb dosing was changed to once every 4 weeks (AUC=6) for the next 17 pts. P+Cb+T was continued until disease progression, unacceptable toxicity, or...