11182 Background: Immune checkpoint inhibitors (ICIs) targeting the PD-1 (Pembrolizumab) and PD-L1 (Atezolizumab) have revolutionized the first-line management of metastatic non-small cell lung cancer (mNSCLC). While these agents are often considered clinically interchangeable, the differences in molecular binding mechanism and tissue-specific penetration may lead to distinct therapeutic patterns. Since the real-world evidence on the propensity for organ-specific metastatic spread remains limited, we aim to compare organ-specific metastatic progression patterns between the two therapies. Methods: We conducted a retrospective cohort study utilizing the TriNetX US Collaborative Network. After identifying adults with stage IV mNSCLC on initial Pembrolizumab or Atezolizumab monotherapy, patients with pre-existing metastases at the specific organ site of interest were excluded. Propensity score matching (1:1) was performed to balance cohorts across demographic and clinical variables. Our endpoints were metastases to the CNS, mediastinum, bone, liver, adrenal glands, and skin over 365 days. Hazard ratios (HR) were estimated using Cox proportional hazards models. Results: Atezolizumab was associated with a significantly higher risk of CNS metastases compared with Pembrolizumab (1-year incidence: 16.9% vs 6.1%; HR 3.08, 95%CI: 2.73-3.46; p 1.0 indicates increased risk with Atezolizumab; HR < 1.0 indicates increased risk with Pembrolizumab.
Nawab et al. (Wed,) studied this question.