Our results support the use of trastuzumab over lapatinib in the HER2 treatment-naive first-line metastatic setting," Gelmon's group stated. "The NCIC CTG MA.31 trial was the first head-to-head comparison to our knowledge of trastuzumab and lapatinib in locally determined metastatic HER2-positive breast cancer, with separate analysis for centrally determined HER2 disease.