Phase II Study of Lapatinib and Trastuzumab Followed by Concurrent Lapatinib, Trastuzumab, and Paclitaxel Followed by Surgery for Primary HER2-positive (HER2+) Breast Cancer

PRIMARY OBJECTIVES: I. To evaluate the changes in cancer stem cell (CSC) markers; % CD44 variant (CD44v)-positive tumor cells and aldehyde dehydrogenase-1 (ALDH1) positivity before and after study drug exposure and after concurrent preoperative chemotherapy. II. To determine the pathological complete response (pCR) rate produced by lapatinib (lapatinib ditosylate) + trastuzumab followed by concurrent preoperative lapatinib, trastuzumab, and paclitaxel chemotherapy for operable human epidermal growth factor receptor 2-positive (HER2+) breast cancer. SECONDARY OBJECTIVES: I. To determine the cellular response rate produced by study drug exposure and/or concurrent preoperative chemotherapy. II. To determine cutoff values of baseline ratios of phosphorylated HER2 (pHER2)/HER2, phosphorylated epidermal growth factor receptor (EGFR) (pEGFR)/EGFR, phosphorylated ERK (pERK)/ERK and phosphorylated protein kinase B (pAkt)/Akt that are associated with pCR. III. To assess the safety and tolerability of study therapy in Japanese women. OUTLINE: Drug exposure: Patients receive lapatinib ditosylate orally (PO) once daily (QD) and trastuzumab intravenously (IV) over 30-90 minutes once weekly for 6 weeks in the absence of disease progression or unacceptable toxicity. Preoperative therapy: Patients receive lapatinib ditosylate PO QD, trastuzumab IV over 30 minutes once weekly, and paclitaxel IV over 90 minutes once weekly for 12 weeks in the absence of disease progression or unacceptable toxicity. Patients then undergo lumpectomy* or mastectomy*. After completion of study treatment, patients are followed up for 12 weeks. NOTE: * Patients considered to be candidates for breast-conservation therapy (BCT) are offered lumpectomy. Patients who are not considered to be candidates for BCT or who do not desire BCT undergo total mastectomy.