Multicenter phase II trial of neoadjuvant carboplatin, weekly nab-paclitaxel, and trastuzumab in stage II-III HER2+ breast cancer: A BrUOG study.

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619 Background: Patients (pts) with human epidermal growth factor receptor-2 amplified (HER2+) breast cancers (BrCa) who achieve a pathologic complete response (pCR) with neoadjuvant chemotherapy (NAC) + trastuzumab (T) have an excellent prognosis (Cortazar, SABCS 2012). We tested a novel NAC + T regimen, designed to avoid potential cardiac and other toxicities associated with anthracyclines (A) and eliminate steroid premedication by replacing standard paclitaxel with nab-paclitaxel (nP). Methods: Clinical stage IIA-IIIC HER2+ BrCa pts received single agent either nP or T, with research biopsies and MRIs obtained before and after, then carboplatin (Cb) AUC 6 q3wks, nP 100 mg/m2and T 2 mg/kg weekly x 18 wks. If present, residual tumor was collected at surgery. Post-op pts complete a year of T; other adjuvant treatment is at MD discretion. Endpoints include clinical + pathologic response (pCR is defined as no invasive BrCa in breast + axillary nodes), residual cancer burden (RCB), treatment delivery and toxicities. Results: 53 pts (of 60 planned) are evaluable for response, median age 51 (34-72). Median delivered dose intensity for nP was 89 mg/m2/week; nP doses were omitted or reduced for neutropenia (ANC) (in 20% of pts) and neurotoxicity (Nt) (5%). Cb was reduced for thrombocytopenia (tcp) in 15%. Grade 3-4 toxicities: ANC 65%, tcp 22%, anemia 37%, Nt 7%. Serious adverse events: febrile neutropenia (5 pts), infections w/o neutropenia (4), vomiting, diarrhea or dehydration (7), thrombosis (2). LVEF fell by >10% in 3 pts with no clinical CHF. Response data are tabulated below: 28 pts (53%) achieved pCR or RCB class I; 15/21 who did not received A-based adjuvant chemotherapy. Of 38 clinically node-positive pts, 26 (68%) were node-negative at surgery. Conclusions: The Cb/nP/T regimen was well tolerated, with pCR rates comparable to those reported with A-containing regimens. Final treatment and response data will be presented; correlative studies will be reported separately. Clinical trial information: NCT00617942. [Table: see text]