- Arm III (lapatinib ditosylate and (trastuzumab [Herceptin®] combination): Patients receive oral lapatinib ditosylate once daily on days 1-11. Within 24 hours after completion of neoadjuvant therapy, patients undergo either breast-conservation surgery or mastectomy, and receive adjuvant lapatinib ditosylate once daily on days 12-28. Patients also receive neoadjuvant trastuzumab IV over 90 minutes on days 1 and 8 and receive adjuvant trastuzumab on day 15.