Use of the FoundationOne next-generation sequencing (NGS) assay to detect actionable alterations leading to clinical benefit of targeted therapies for relapsed and refractory breast cancer.

1009 Background: Genomically-informed cancer therapy linking therapeutics targeting the molecular alterations driving the malignancy has the potential to transform the care of patients with metastatic breast cancer (MBC). Methods: DNA was isolated from 4 FFPE sections cut at 10 microns from 177 consecutive MBC that had relapsed after surgery, conventional hormonal/chemo and anti-HER2 targeted therapies received by our CLIA lab (Foundation Medicine). DNA sequencing was performed for 3,320 exons of 182 cancer-related genes to average depth of 1017X. Actionable Genomic alterations (GA) were defined as those linked to targeted anti-cancer therapies approved or being evaluated in active registered clinical trials. Results: Genomic profiles were generated from 169/177 (95%) BCs identifying 565 GA, averaging 3.34 GAs per tumor (range 0 to 10). 152 (90%) tumors harbored an actionable alteration mean 1.88 per tumor (range 0 to 6). In 124 (73%) tumors, ≥1.0 actionable GA was detected that would be missed by current...