Abstract only 9091 Background: To determine real-world outcomes with first line pembrolizumab monotherapy, for aNSCLC with PD-L1 TPS ≥50%. Methods: Bispective, national and multicentric study including consecutively aNSCLC patients who initiated first-line pembrolizumab monotherapy from May 5, 2017 (marketing authorization of pembrolizumab monotherapy in France) to Nov 22, 2019 (marketing authorization of pembrolizumab-chemotherapy for non-squamous aNSCLC). Data were collected on medical charts. Responses were locally assessed according to RECIST v1.1; overall survival (OS) and real-world progression-free survival (rwPFS) were assessed by Kaplan-Meier method. Results: 845 patients (pts) were included by 33 centres: 67.8% were men, PS 0/1/≥2: 25.5%/46.9%/27.6%, active/former/nonsmokers: 39.1%/51.7%/6.4%, adenocarcinoma: 70.8%; stage IV at diagnosis: 91.6%; median number of metastatic sites at baseline: 2±1 (brain (20.8%), liver (13.9%) and bone (35%)); KRAS mutated: 27.7%, PDL1 TPS > 75%: 53.7% At the cut off date (31 December 2020), on the 783/845 (92.7%) evaluable pts, CR, PR, disease stabilization and progression were reported on 4.7%, 42.6%, 24.1% and 28.6% of cases, respectively; 588 (69.6%) pts had discontinued pembrolizumab, 390 (66.4%) had a first disease progression; 320/390 (82.1%) received a second line treatment, mainly platinum-based chemotherapy (90.6%). With a median follow up of 25,8 95%CI: 24,8-26,7 months, median rwPFS and median OS were 8,2 95%CI: 6,9-9,5 and 22,6 95%CI: 18,5-27,4 months, respectively; 6, 12, 18-months survival rates were 76,8%, 64,8% and 54,3%. 835 adverse events were reported in 48% of the patients, grade ≥3 in 13.8% of cases, mainly asthenia, colitis, pneumonitis. For evaluable patients receiving a platinum-based doublet in second line (266/290, 89%), CR, PR, disease stabilization and progression were reported on 1.9%, 41%, 35.3% and 21.8% of cases, respectively. Uni and multivariate analysis of factors related to OS will be presented at the congress. Conclusions: Despite a less stringent selection of patients, pembrolizumab as a single agent achieves similar tumor shrinkage, rwPFS and OS than those of pivotal clinical trials.