PROJECT SUMMARY/ABSTRACT Despite recent advances in the treatment of head and neck squamous cell carcinoma (HNSCC), five-year overall survival (OS) has remained poor due to high rates of disease progression after treatment. A lack of reliable prognostic biomarkers limits our ability to predict disease progression in non-human papillomavirus (HPV) mediated HNSCC. Even among candidates for salvage surgery in the setting of disease progression after primary chemoradiotherapy (CRT), 5-year OS is estimated at just 16%. Radiomics, which involves the analysis of large numbers of quantitative tumor imaging features, has been recently used to develop image-based prognostic models. More specifically, delta radiomics incorporates differences between pre- and post-treatment images, thereby capturing quantitative measures of treatment response. To address the critical need for prognostic biomarkers for patients with HNSCC, we aim to develop and validate radiogenomics models to predict 2-year overall and progression-free survival using gene expression, ctDNA and delta radiomic data. Prior studies have developed highly accurate models of cancer treatment response using delta radiomics, but not in patients with locoregionally advanced HNSCC. Furthermore, few studies have evaluated reliable and concordant genomic and radiomic prognostic phenotypes in HNSCC. In this study, we hypothesize that a radiogenomics model will accurately predict 2-year overall and progression-free survival. To advance the overall objective of this study, we will pursue the following two Specific Aims. Our first aim is to 1) develop a fully annotated, patient- centered, clinical outcome and radiographic dataset with associated biospecimen samples for patients with locoregionally advanced HPV-negative HNSCC treated with definitive CRT. Our second aim is to use liquid based-biopsy biomarkers, gene expression data, and delta radiomic features derived from pre- and post- treatment imaging to predict 2-year OS and PFS in patients with locoregionally advanced HPV-negative HNSCC treated with definitive CRT. We will extract delta radiomics features and measure transcription of ~1,800 genes in the Cancer Transcriptome Atlas using digital spatial profiling, focusing on genes relevant to epidermal growth factor receptor, MAPK-associated protein kinase 2 (MK2) and hypoxia pathways. We will then measure circulating tumor DNA (ctDNA) using banked pre- and post-treatment plasma samples. This will enable us to explore radiogenomics phenotypes associated with 2-year OS and PFS in patients with HNSCC treated with CRT. The long-term goal of this work is to support future clinical trials aimed at early identification of patients at high-risk of disease progression who are likely to benefit from intensified, precision treatment approaches.