Abstract
533 Background: The aim of this study was to compare the extent of pathologic response in HER2-positive patients treated with standard neoadjuvant chemotherapy with or without trastuzumab according to hormone receptor (HR) status. Methods: The study included 199 patients with HER2-positive disease treated in clinical trials of neoadjuvant chemotherapy. Eighty-nine patients treated with 3- weekly paclitaxel and concurrent trastuzumab followed by 5-fluorouracil, epirubicin, and cyclophosphamide (FEC) were compared with 110 patients treated with weekly or 3-weekly paclitaxel followed by FEC or FAC. Residual cancer burden (RCB), a measurement of residual disease (RD) from pathologic review of the primary tumor and lymph nodes, was classified as pathologic complete response (pCR), RCB-I (near-pCR, minimal RD), RCB-II (moderate RD), or RCB-III (extensive RD). RCB was compared between treatment groups according to HR status. Results: In HR-negative patients, similar pCR rates were achieved with weekly T/FAC as with 3-weekly T/FEC and trastuzumab (61% and 65%, respectively). However, in HR-positive patients, higher pCR rates were achieved with 3-weekly T/FEC and trastuzumab (47%) than with the weekly T/FAC (25%; p=0.04) or 3-weekly T/FAC (19%; p=0.01) ( Table 1 ). Near pCR (RCB-I) was slightly higher in HR-positive (26%) than in HR-negative patients treated with 3-weekly T/FEC and trastuzumab (11%; p=0.07). Conclusions: Patients with HR- negative/HER2-positive breast cancer had similar pathologic response rates from addition of trastuzumab to 3-weekly T/FEC or from weekly T/FAC chemotherapy. Patients with HR-positive/HER2-positive breast cancer obtained significant benefit from addition of trastuzumab to 3- weekly T/FEC, compared to 3-weekly T/FAC or weekly T/FAC. The combination of weekly T/FEC with trastuzumab as neoadjuvant chemotherapy should be evaluated. [Table: see text] [Table: see text]
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