A retrospective real-world study of first-line PD-(L)1 inhibitor use in patients with metastatic non-small cell lung cancer (mNSCLC).

e20563 Background: Programmed death ligand 1 (PD-[L]1) inhibitors such as retifanlimab have improved survival in patients with mNSCLC, yet these treatments may still be underutilized. This study examined treatment patterns and factors associated with selection of a PD-(L)1 inhibitor in first-line (1L) treatment regimens among patients with mNSCLC who were not candidates for targeted therapies. Methods: A retrospective cohort study was conducted among US patients diagnosed with mNSCLC using the nationwide Flatiron Health electronic health record (EHR)-derived deidentified database. The Flatiron Health database is a longitudinal database, comprising patient-level structured and unstructured data, curated via technology-enabled abstraction. Eligible patients had a diagnosis of mNSCLC not treatable with a targeted therapy on or after January 1, 2019, and who initiated 1L treatment on or after July 1, 2019. Treatment regimens were classified dichotomously based on whether the regimen contained an approved PD-(L)1 inhibitor. Descriptive statistics were used to summarize treatment patterns and patient and disease characteristics. A multivariable logistic regression model was used to explore factors associated with use or nonuse of a 1L regimen that contained a PD-(L)1 inhibitor. Results: 13,223 patients met the eligibility criteria, which were modeled after a multiregional phase 3 clinical trial in the same patient population (POD1UM-304; NCT04205812). Among the overall population, median (Q1, Q3) age was 70 (63, 77) years; the majority of patients were male (54%), White (66%), non-Hispanic (69%), had a history of smoking (92%), had an ECOG PS of 1 (42%) or 0 (24%), and were treated at a community clinic (81%). Nonsquamous histology constituted 71% of tumors. Overall, 25% of the study population did not receive a PD-(L)1 inhibitor in the 1L setting. This finding was consistent across all study years (2019-2023). Platinum-based chemotherapy was the most common 1L treatment administered to patients who did not receive a PD-(L)1 inhibitor. Logistic regression model found the following factors to be statistically significantly associated ( P <0.05) with the likelihood of receiving a PD-(L)1 inhibitor in the 1L mNSCLC setting compared with a 1L regimen that did not contain a PD-(L)1 inhibitor: age, ethnicity, smoking status, year of metastatic diagnosis, prior treatment with a PD-(L)1 inhibitor, PD-(L)1 staining status, stage at initial diagnosis, practice type, and region. Conclusions: The study demonstrated that there continues to be a large proportion of US patients with mNSCLC receiving 1L regimens that do not include approved PD-(L)1 inhibitors, despite their widespread availability and incorporation into clinical guidelines as the preferred frontline therapy. Findings suggest that nonuse of a PD-(L)1 inhibitor is influenced by both clinical and structural factors.