Background: MRD aims to detect circulating biomarkers of micrometastatic disease and ultimately predict recurrences. The IFCT-0703 randomized phase II trial failed to show a benefit of 6 months adjuvant pazopanib (P) vs. placebo after resection of stage I NSCLC (7th TNM edition). The outcome of pts based on their MRD status has been evaluated. Methods: Blood samples were collected in EDTA tubes (Becton Dickinson Company) after surgery (T0), after 3 months (T3) of P or placebo and at the end of treatment (T6). Plasmas were obtained after double centrifugation of total blood. Total nucleic acid was extracted using the Maxwell RSC LV plasma kit (Promega) according to the manufacturer’s protocol. Samples were quantified using the QuBit dsDNA HS Assay kit on a QuBit 3.0 flurometer (Thermo Fisher Scientific). Molecular analysis was performed by next generation sequencing using the Oncomine Lung cfDNA Assay (ThermoFisher Scientific). Two MRD definitions were tested : 1) high level of DNA in the blood or 2) any mutation detected by the standard bioinformatic pipeline was considered present, whatever the allelic fraction. Results: 143 pts were randomized in 29 centers between March 2009 and August 2012, 71 and 72 in the placebo and P arms respectively. Among the 119 pts with evaluable T0 samples, 27 pts recurred and 14 died. Median DNA concentration ([DNA]) was 6.6 ng/ml and an increase of [DNA] of 10 ng/ml was found prognostic of poor DFS and OS, HR=1.4, 95%CI [1.14-1.72], p=0.0016 and HR=1.62, 95%CI [1.15-2.30], p=0.0057 respectively. In 81 pts with available T0-T6 samples, [DNA] variation had no different impact on DFS and OS, in the P arm and the placebo arm. ctDNA mutations (ctDNA+) were detected in 31/119 pts. ctDNA+ were more frequent in samples with high DNA quantity (p=0.0002). Genes mutated at T0 were TP53 in 16, NRAS in 6, MAP2K1 in 2, KRAS in 1, EGFR in 5, BRAF in 1, ALK in 2. 29 pts had 1 mutation, 2 had 2 mutations. DFS and OS were similar between pts with or without ctDNA+ : HR= 1.038 (95%CI 0.438-2.456, p=0.93) and 1.193 (95% CI 0.367-3.882, p=0.77) respectively. Among 27 pts with ctDNA+ at T0 and available sample at T6, 23 had no more mutations at T6. Two pts had a ctDNA+ only at T6 (not at T3), one of them had a recurrence at 7 months. Conclusions: Post-operative ctDNA mutations are found in 26.0% of the pts but their positivity had no impact on DFS or OS. In contrast, DFS and OS were poorer in pts with increased plasma DNA concentration. ctDNA mutations status do not recapitulate the complexity of MRD characterization. NGS will be performed on matched tissues in order to refine MRD definition. Clinical trial information: NCT00775307