Individual patient-level data were obtained from all seven identified, relevant trials (table),4, 5, 6, 7, 8, 9, 10 providing data for 13 864 women with early-stage, HER2-positive breast cancer who had been randomly assigned to receive chemotherapy plus trastuzumab or chemotherapy alone between February, 2000, and December, 2005. The gene discussed is ERBB2; the disease is breast cancer.