Tolerability of the Combination of Lapatinib and Trastuzumab in Adults Age 60 or Older With HER2 Positive Locally Advanced or Metastatic Breast Cancer

This phase II trial studies the side effects and how well lapatinib ditosylate and trastuzumab work in treating older patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer that has spread from where it started to nearby tissue or lymph nodes (locally advanced) or to other parts of the body (metastatic). Lapatinib ditosylate may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Monoclonal antibodies, such as trastuzumab, can block tumor growth in different ways. Some block the ability of tumor to grow and spread. Others find tumor cells and help kill them or tumor cancer-killing substances to them. Giving lapatinib ditosylate together with trastuzumab may kill more tumor cells.