HER2-related biomarkers in HER2+ breast cancer patients in Asia Pacific

초록

Recent findings suggest that HER2-related molecular markers such as PTEN deletion or downregulation, PIK3CA mutation, truncated HER2 receptor (p95HER2), and tumor HER2 mRNA levels, have the potential to predict anti-HER2 treatment response. We evaluated the distribution of these biomarkers and their relationship to responsiveness to lapatinib treatment in the metastatic setting in HER2+ breast cancer patients. We also explored the conversion or conservation rates of relevant biomarkers between primary diagnosis and at recurrence or metastasis. Observational study of female HER2+ breast cancer patients who were initiated on lapatinib treatment following recurrence or metastases in five Asia Pacific countries between Aug 2010 and Dec 2012. Eligible patients: Had a tumor biopsy specimen available from their primary breast cancer diagnosis or before they started on any anti-HER2 treatment Had not been exposed to more than two lines of trastuzumab-based regimen in the metastatic setting prior to start of lapatinib-based regimen or other experimental anti-HER2 treatment Had no other primary tumor p95HER2 expression was evaluated by immunohistochemistry (IHC) assay by bioMerieux. PTEN levels were assessed by IHC and PIK3CA mutations were detected by a mass spectroscopy-based approach. Tumor HER2 mRNA results were not available at the time of poster preparation. The primary endpoint was progression-free survival (PFS) from the initiation of first lapatinib-based regimen given in metastatic setting to disease progression from that regimen or death from any cause, calculated up to 31 Aug 2013. Our findings suggest that p95HER2 expression may be predictive of clinical response to lapatinib treatment in HER2+ breast cancer patients – these remain to be confirmed with the complete p95HER2 results together with tumor HER2 mRNA results. Among patients with available data, p95HER2 status and PIK3CA status remained unchanged with disease progression for the