PIK3CA mutation analysis in recurrent breast cancer

11041 Background: Mutations in PIK3CA (encoding p110α catalytic subunit of phosphatidylinositol-3-kinase) are among the most common genetic events identified in breast cancer but the role of these mutations in determining the clinical course of the disease is uncertain. Furthermore the frequency of PIK3CA mutation in metastatic breast cancer samples has not been adequately studied but is an important concern in the design of studies with novel agents designed to inhibit mutant PIK3CA. Methods: We have established a tumor banking protocol for patients (pts) with metastatic breast cancer. In this study, we performed a mutational analysis of exons 9 (HD) and 20 (KD) of the PIK3CA using tumor DNA obtained from pts with recurrent disease and correlated mutational status with clinicopathological features and prognosis. Results: Biopsies were obtained from sites of recurrence in 51 pts with stage 4 disease. The median F/U was 44 (range: 0.9–239) months and death has occurred in 66%. Mutations in PIK3CA were iden...