Neoadjuvant Trastuzumab and Letrozole for Postmenopausal Women

Eligibility criteria * Ages Eligible for Study: ≥ 20 years * Invasive cancer (clinical stage IB-IIIB) * Measurable tumor larger than 1cm * ECOG status 0 or 1 * Postmenopausal women * Age ≥55 years and amenorrhea * Age \<55 years and amenorrhea for ≥12 months with FSH \>30 mIU/ml * HER2 positive tumor * 3 positive on IHC * 2 positive on IHC with HER2 gene amplification on FISH or SISH using a single-probe or dual-probe * Estrogen receptor positive tumor * Positive ER expression with Allred score more than PS3/TS8 or modified Allred score more than PS4/TS7 * Eligible cardiac function * Normal heard evaluated by ECG * Consider clinically non-significant arrythmia and ischemic change as normal * LVEF ≥ 55% measured by ECHO or MUGA scan Outcome measures * Primary End-point * The rate of pathologic complete response (pCR) * No residual invasive cancer in breast * Secondary End-point * Clinical Response Rate * Safety profiles for the preoperative use of concurrent trastuzumab and letrozole * The rate of breast conservative surgery * Total pathologic complete response (tpCR) * No residual invasive cancer in breast and ipsilateral axilla * Analysis of biomarkers based on baseline specimen and residual tumor * Ki67 expression * cDNA microarray: gene expression profiling * Association between clinical response rate and circulating tumor cells (CTCs) * CTCs are measured by CytoGen (SEOUL, KOREA)"