ERBB2 and breast cancer: The objective of this study was to compare DFS in patients with HER2 overexpressing and/or amplified breast cancer randomized to trastuzumab for 1 year versus lapatinib for 1 year versus trastuzumab (12 weeks) followed by a 6-week treatment-free interval followed by lapatinib (34 weeks) versus trastuzumab in combination with lapatinib for 1 year.