P15 Indirect Treatment Comparisons of Time-to-Event Outcomes with Mis-Matched "Time Zero": Methodology and Application in Resectable Non-Small Cell Lung Cancer

Immune checkpoint inhibitors have recently been approved for resectable non-small cell lung cancer (rNSCLC): neoadjuvant nivolumab plus chemotherapy (CT) (neoNIVO+CT), and adjuvant atezolizumab (adjATEZO) as treatment following resection and adjuvant CT (adjCT). Head-to-head comparisons are unavailable and differences in "time-zero” across trials preclude traditional indirect treatment comparisons (ITC). Our objective was to develop a method that adjusts for differences in time-zero, to incorporate into an ITC of event-free survival (EFS) between neoNIVO+CT and adjATEZO among patients with stage II-IIIA rNSCLC whose tumours express programmed death ligand-1 (PD-L1) ≥ 50% or PD-L1 ≥ 1%.