Next generation sequencing of cell free circulating tumor DNA in blood samples of recurrent and metastatic head and neck cancer patients.

e17516Background: Head and Neck Squamous Cell Carcinoma (HNSCC) is an increasingly prevalent disease but effective targeted therapy is lacking. The use of next generation sequencing (NGS) in the identification of novel targets has been suggested as a way to potentially expand therapeutic options and thereby improve outcomes. Methods: Data was collected on patients with recurrent and metastatic (R/M) head and neck cancers who underwent molecular profiling of blood samples utilizing Guardant360, a 70-gene circulating tumor DNA (ctDNA) NGS platform. CtDNA sequencing data was compared to tumor NGS data, when available. Best response to therapy was assessed using RECIST measures. Results: 60 HNSCC patients were evaluated from February 2015 to June 2016. The most common tumor type and histology was oropharyngeal squamous cell carcinoma (n = 21), which was commonly human papillomavirus (HPV) positive (n = 15). Other cancer types included salivary gland and thyroid cancers. The most common mutations identified by...