A PHASE III, OPEN-LABEL, RANDOMIZED STUDY TO INVESTIGATE THE EFFICACY AND SAFETY OF ATEZOLIZUMAB (ANTI−PD-L1 ANTIBODY) COMPARED WITH BEST SUPPORTIVE CARE FOLLOWING ADJUVANT CISPLATIN-BASED CHEMOTHERAPY IN PATIENTS WITH COMPLETELY RESECTED STAGE IB−IIIA NON−SMALL CELL LUNG CANCER