1264P Early circulating tumour DNA (ctDNA) dynamics for predicting and monitoring response to immunotherapy (IO) vs chemotherapy (CT) in patients with 1L metastatic (m) NSCLC: Analyses from the phase III MYSTIC trial

We have previously shown that ctDNA dynamics can identify pts as “molecular responders” (MRs) to IO who have improved OS compared with molecular non-responders (non-MRs). Larger randomized studies in specific clinical settings including 1L are needed to optimize use of ctDNA as a biomarker of response. We report analyses of ctDNA in pts with mNSCLC treated with 1L durvalumab (D), D + tremelimumab (T), or CT in the phase III MYSTIC trial (NCT02453282).