Loss of Phosphatase and Tensin Homolog or Phosphoinositol-3 Kinase Activation and Response to Trastuzumab or Lapatinib in Human Epidermal Growth Factor Receptor 2–Overexpressing Locally Advanced Breast Cancers

Abstract

Activation of PI3 kinase pathway is associated with trastuzumab resistance, whereas low PTEN predicted for response to lapatinib. These observations support clinical trials with the combination of both agents.