Nearly half of non-small cell lung cancer patients are diagnosed with localized disease, making them candidates for chemoradiotherapy (CRT) as curative treatment. Among these, CRT is the main treatment for stage III patients, of whom, ~30% will experience local recurrence. Despite advances utilizing tumor imaging techniques to improve targeting, no further personalization is done based on tumor biology to refine radiation strategy. Therefore, relevant biomarkers to predict treatment outcome to guide and adapt CRT are lacking. In our lab, we address this problem by profiling cell-free DNA using state-of-the-art techniques to infer RNA expression from DNA, and thereby identify determinants of response to CRT.