Pertuzumab may also be effective in cases of normal levels of HER2 with high HER1 (EGFR) levels, or breast cancers with characteristics of low-level HER2 overexpression.101,102 So far, efficacy of pertuzumab for HER2-positive metastatic disease has been successfully confirmed in clinical trials. Here, EGFR is linked to metastatic neoplasm.