SAN ANTONIO (EGMN) - Two biomarkers may help predict which HER2-positive tumors are resistant to trastuzumab, and one may predict response to lapatinib, findings that could lead the way to better tailored therapy for women with this type of breast cancer.Low phosphatase and tensin homolog (PTEN) expression and mutations in phosphoinositide 3-kinase (PI3K) appear to predict resistance to trastuzumab (Herceptin), and low PTEN appears to predict lapatinib (Tykerb) response, Dr. Jenny Chang reported...