PEmbRolizumab verSus chEmotherapy and pEmbrolizumab in Non-small-cell Lung Cancers (NSCLC) With PDL1 ≥ 50 %

PERSEE is a french academic, prospective, randomized, controlled and open-label phase 3 study. This trial compares the combination of chemotherapy and pembrolizumab with pembrolizumab alone as first-line treatment for advanced NSCLC molecularly characterized by a PDL1 expression level ≥ 50% and no EGFR mutations or ALK rearrangement. This is a strategy trial whose primary objective is to evaluate the superiority of the chemotherapy-pembrolizumab combination over pembrolizumab using PFS as the primary endpoint as evaluated by an independent review committee. PERSEE trial is planned to include 292 patients treated at approximately 30 GFPC-affiliated or GFPC-associated centres. After the screening period, patients will be randomized on a 1:1 basis to the Chemotherapy Immunotherapy Arm or the Immunotherapy Arm. Randomization will be stratified according to tumor histology (squamous versus non squamous) and according to the presence or absence of brain metastases. Patients enrolled in this study will receive either of the following treatment regimens: 1. Chemotherapy-Immunotherapy Arm: Four induction cycles once every 3 weeks associating, on the first day of each cycle: * Cisplatin 75 mg/m² or carboplatin area under the curve (AUC) 5 mg/mL/min, pemetrexed 500 mg/m² and pembrolizumab 200 mg for non-squamous NSCLC. * Carboplatin AUC 6 mg/mL/min, paclitaxel 200 mg/m² and pembrolizumab 200 mg for squamous NSCLC. After the 4 induction cycles, a maintenance therapy will be possible for patients who are responding or stable, as follows: * Non squamous NSCLC: pembrolizumab and pemetrexed combination or either drug as monotherapy (if toxicity has been identified for one of them). * Squamous NSCLC: pembrolizumab monotherapy. For pembrolizumab: treatment may be continued for a maximum of 35 cycles or until disease progression, death, unacceptable toxicity, or following the Investigator's or the patient's decision to stop. For pemetrexed, treatment may be continued until disease progression, death, unacceptable toxicity, or following the Investigator's or the patient's decision to stop. 2. Immunotherapy Arm: Pembrolizumab 200 mg once every 3 weeks for a maximum of 35 cycles or until disease progression, death, unacceptable toxicity, or the Investigator's or the patient's decision to stop. Evaluations will be performed every 6 weeks (±7 days) during the first 4 cycles in both treatment arms, then every 9 weeks (±7 days) for the first 12 months since D1 of cycle 1 and every 12 weeks (±7 days) thereafter. Evaluations will include: tumor assessment according to RECIST v1.1, survival status, concomitant medications and AE recording. QoL/PRO questionnaires will be performed at each cycle for the first 5 cycles in both treatment arms, then every 9 weeks (±7 days) for the first 12 months since D1 of cycle 1 and every 12 weeks (±7 days) thereafter. The length of the inclusion period is 36 months (3 years). The total study duration per patient will be a maximum of two years for the last patients included, and a maximum of five years for the first patients included (i.e. End-of-study Time Point for surviving patients) The total study duration includes the following: * Screening Period: up to 28 days. * Treatment Period: up to 60 months. * Post-study Follow up Period: until death or lost to follow-up.